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-protocol/src/lib.rs

@@ -22,7 +22,7 @@ mod tests;
 pub mod test_util;
 
 use nu_protocol::{
-    ast::Operator, engine::Closure, Config, LabeledError, PipelineData, PluginSignature, RawStream,
+    ast::Operator, engine::Closure, Config, LabeledError, PipelineData, PluginSignature,
     ShellError, Span, Spanned, Value,
 };
 use serde::{Deserialize, Serialize};
@@ -82,32 +82,20 @@ pub enum PipelineDataHeader {
     ///
     /// Items are sent via [`StreamData`]
     ListStream(ListStreamInfo),
-    /// Initiate [`nu_protocol::PipelineData::ExternalStream`].
+    /// Initiate [`nu_protocol::PipelineData::ByteStream`].
     ///
     /// Items are sent via [`StreamData`]
-    ExternalStream(ExternalStreamInfo),
+    ByteStream(ByteStreamInfo),
 }
 
 impl PipelineDataHeader {
-    /// Return a list of stream IDs embedded in the header
-    pub fn stream_ids(&self) -> Vec<StreamId> {
+    /// Return the stream ID, if any, embedded in the header
+    pub fn stream_id(&self) -> Option<StreamId> {
         match self {
-            PipelineDataHeader::Empty => vec![],
-            PipelineDataHeader::Value(_) => vec![],
-            PipelineDataHeader::ListStream(info) => vec![info.id],
-            PipelineDataHeader::ExternalStream(info) => {
-                let mut out = vec![];
-                if let Some(stdout) = &info.stdout {
-                    out.push(stdout.id);
-                }
-                if let Some(stderr) = &info.stderr {
-                    out.push(stderr.id);
-                }
-                if let Some(exit_code) = &info.exit_code {
-                    out.push(exit_code.id);
-                }
-                out
-            }
+            PipelineDataHeader::Empty => None,
+            PipelineDataHeader::Value(_) => None,
+            PipelineDataHeader::ListStream(info) => Some(info.id),
+            PipelineDataHeader::ByteStream(info) => Some(info.id),
         }
     }
 }
@@ -119,32 +107,11 @@ pub struct ListStreamInfo {
     pub span: Span,
 }
 
-/// Additional information about external streams
+/// Additional information about byte streams
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
-pub struct ExternalStreamInfo {
-    pub span: Span,
-    pub stdout: Option<RawStreamInfo>,
-    pub stderr: Option<RawStreamInfo>,
-    pub exit_code: Option<ListStreamInfo>,
-    pub trim_end_newline: bool,
-}
-
-/// Additional information about raw (byte) streams
-#[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
-pub struct RawStreamInfo {
+pub struct ByteStreamInfo {
     pub id: StreamId,
-    pub is_binary: bool,
-    pub known_size: Option<u64>,
-}
-
-impl RawStreamInfo {
-    pub fn new(id: StreamId, stream: &RawStream) -> Self {
-        RawStreamInfo {
-            id,
-            is_binary: stream.is_binary,
-            known_size: stream.known_size,
-        }
-    }
+    pub span: Span,
 }
 
 /// Calls that a plugin can execute. The type parameter determines the input type.
@@ -380,7 +347,7 @@ impl PluginCallResponse<PipelineData> {
                 PipelineData::Empty => false,
                 PipelineData::Value(..) => false,
                 PipelineData::ListStream(..) => true,
-                PipelineData::ExternalStream { .. } => true,
+                PipelineData::ByteStream(..) => true,
             },
             _ => false,
         }