Replace ExternalStream with new ByteStream type (#12774)

# Description
This PR introduces a `ByteStream` type which is a `Read`-able stream of
bytes. Internally, it has an enum over three different byte stream
sources:
```rust
pub enum ByteStreamSource {
    Read(Box<dyn Read + Send + 'static>),
    File(File),
    Child(ChildProcess),
}
```

This is in comparison to the current `RawStream` type, which is an
`Iterator<Item = Vec<u8>>` and has to allocate for each read chunk.

Currently, `PipelineData::ExternalStream` serves a weird dual role where
it is either external command output or a wrapper around `RawStream`.
`ByteStream` makes this distinction more clear (via `ByteStreamSource`)
and replaces `PipelineData::ExternalStream` in this PR:
```rust
pub enum PipelineData {
    Empty,
    Value(Value, Option<PipelineMetadata>),
    ListStream(ListStream, Option<PipelineMetadata>),
    ByteStream(ByteStream, Option<PipelineMetadata>),
}
```

The PR is relatively large, but a decent amount of it is just repetitive
changes.

This PR fixes #7017, fixes #10763, and fixes #12369.

This PR also improves performance when piping external commands. Nushell
should, in most cases, have competitive pipeline throughput compared to,
e.g., bash.
| Command | Before (MB/s) | After (MB/s) | Bash (MB/s) |
| -------------------------------------------------- | -------------:|
------------:| -----------:|
| `throughput \| rg 'x'` | 3059 | 3744 | 3739 |
| `throughput \| nu --testbin relay o> /dev/null` | 3508 | 8087 | 8136 |

# User-Facing Changes
- This is a breaking change for the plugin communication protocol,
because the `ExternalStreamInfo` was replaced with `ByteStreamInfo`.
Plugins now only have to deal with a single input stream, as opposed to
the previous three streams: stdout, stderr, and exit code.
- The output of `describe` has been changed for external/byte streams.
- Temporary breaking change: `bytes starts-with` no longer works with
byte streams. This is to keep the PR smaller, and `bytes ends-with`
already does not work on byte streams.
- If a process core dumped, then instead of having a `Value::Error` in
the `exit_code` column of the output returned from `complete`, it now is
a `Value::Int` with the negation of the signal number.

# After Submitting
- Update docs and book as necessary
- Release notes (e.g., plugin protocol changes)
- Adapt/convert commands to work with byte streams (high priority is
`str length`, `bytes starts-with`, and maybe `bytes ends-with`).
- Refactor the `tee` code, Devyn has already done some work on this.

---------

Co-authored-by: Devyn Cairns <devyn.cairns@gmail.com>

crates/nu-plugin/src/plugin/command.rs

@@ -313,7 +313,7 @@ where
         // Unwrap the PipelineData from input, consuming the potential stream, and pass it to the
         // simpler signature in Plugin
         let span = input.span().unwrap_or(call.head);
-        let input_value = input.into_value(span);
+        let input_value = input.into_value(span)?;
         // Wrap the output in PipelineData::Value
         <Self as SimplePluginCommand>::run(self, plugin, engine, call, &input_value)
             .map(|value| PipelineData::Value(value, None))

crates/nu-plugin/src/plugin/interface/mod.rs

@@ -345,7 +345,7 @@ impl InterfaceManager for EngineInterfaceManager {
                 });
                 Ok(PipelineData::ListStream(stream, meta))
             }
-            PipelineData::Empty | PipelineData::ExternalStream { .. } => Ok(data),
+            PipelineData::Empty | PipelineData::ByteStream(..) => Ok(data),
         }
     }
 }
@@ -850,7 +850,7 @@ impl EngineInterface {
         let input = input.map_or_else(|| PipelineData::Empty, |v| PipelineData::Value(v, None));
         let output = self.eval_closure_with_stream(closure, positional, input, true, false)?;
         // Unwrap an error value
-        match output.into_value(closure.span) {
+        match output.into_value(closure.span)? {
             Value::Error { error, .. } => Err(*error),
             value => Ok(value),
         }
@@ -920,7 +920,7 @@ impl Interface for EngineInterface {
                 });
                 Ok(PipelineData::ListStream(stream, meta))
             }
-            PipelineData::Empty | PipelineData::ExternalStream { .. } => Ok(data),
+            PipelineData::Empty | PipelineData::ByteStream(..) => Ok(data),
         }
     }
 }

crates/nu-plugin/src/plugin/interface/tests.rs

@@ -4,10 +4,9 @@ use super::{EngineInterfaceManager, ReceivedPluginCall};
 use nu_plugin_core::{interface_test_util::TestCase, Interface, InterfaceManager};
 use nu_plugin_protocol::{
     test_util::{expected_test_custom_value, test_plugin_custom_value, TestCustomValue},
-    CallInfo, CustomValueOp, EngineCall, EngineCallId, EngineCallResponse, EvaluatedCall,
-    ExternalStreamInfo, ListStreamInfo, PipelineDataHeader, PluginCall, PluginCallResponse,
-    PluginCustomValue, PluginInput, PluginOutput, Protocol, ProtocolInfo, RawStreamInfo,
-    StreamData,
+    ByteStreamInfo, CallInfo, CustomValueOp, EngineCall, EngineCallId, EngineCallResponse,
+    EvaluatedCall, ListStreamInfo, PipelineDataHeader, PluginCall, PluginCallResponse,
+    PluginCustomValue, PluginInput, PluginOutput, Protocol, ProtocolInfo, StreamData,
 };
 use nu_protocol::{
     engine::Closure, Config, CustomValue, IntoInterruptiblePipelineData, LabeledError,
@@ -158,16 +157,9 @@ fn manager_consume_all_propagates_message_error_to_readers() -> Result<(), Shell
     test.add(invalid_input());
 
     let stream = manager.read_pipeline_data(
-        PipelineDataHeader::ExternalStream(ExternalStreamInfo {
+        PipelineDataHeader::ByteStream(ByteStreamInfo {
+            id: 0,
             span: Span::test_data(),
-            stdout: Some(RawStreamInfo {
-                id: 0,
-                is_binary: false,
-                known_size: None,
-            }),
-            stderr: None,
-            exit_code: None,
-            trim_end_newline: false,
         }),
         None,
     )?;
@@ -1046,7 +1038,7 @@ fn interface_eval_closure_with_stream() -> Result<(), ShellError> {
             true,
             false,
         )?
-        .into_value(Span::test_data());
+        .into_value(Span::test_data())?;
 
     assert_eq!(Value::test_int(2), result);
 

crates/nu-plugin/src/plugin/mod.rs

@@ -30,7 +30,7 @@ pub use interface::{EngineInterface, EngineInterfaceManager};
 
 /// This should be larger than the largest commonly sent message to avoid excessive fragmentation.
 ///
-/// The buffers coming from external streams are typically each 8192 bytes, so double that.
+/// The buffers coming from byte streams are typically each 8192 bytes, so double that.
 #[allow(dead_code)]
 pub(crate) const OUTPUT_BUFFER_SIZE: usize = 16384;