Add command_prelude module (#12291)

# Description
When implementing a `Command`, one must also import all the types
present in the function signatures for `Command`. This makes it so that
we often import the same set of types in each command implementation
file. E.g., something like this:
```rust
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
    record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, PipelineData,
    ShellError, Signature, Span, Type, Value,
};
```

This PR adds the `nu_engine::command_prelude` module which contains the
necessary and commonly used types to implement a `Command`:
```rust
// command_prelude.rs
pub use crate::CallExt;
pub use nu_protocol::{
    ast::{Call, CellPath},
    engine::{Command, EngineState, Stack},
    record, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData, IntoSpanned,
    PipelineData, Record, ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
};
```

This should reduce the boilerplate needed to implement a command and
also gives us a place to track the breadth of the `Command` API. I tried
to be conservative with what went into the prelude modules, since it
might be hard/annoying to remove items from the prelude in the future.
Let me know if something should be included or excluded.

src/command.rs

@@ -1,12 +1,9 @@
-use nu_engine::{get_full_help, CallExt};
-use nu_parser::parse;
-use nu_parser::{escape_for_script_arg, escape_quote_string};
-use nu_protocol::report_error;
+use nu_engine::{command_prelude::*, get_full_help};
+use nu_parser::{escape_for_script_arg, escape_quote_string, parse};
 use nu_protocol::{
-    ast::{Call, Expr, Expression},
-    engine::{Command, EngineState, Stack, StateWorkingSet},
-    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Spanned, SyntaxShape,
-    Value,
+    ast::{Expr, Expression},
+    engine::StateWorkingSet,
+    report_error,
 };
 use nu_utils::stdout_write_all_and_flush;
 

src/config_files.rs

@@ -3,15 +3,18 @@ use log::info;
 use nu_cli::read_plugin_file;
 use nu_cli::{eval_config_contents, eval_source};
 use nu_path::canonicalize_with;
-use nu_protocol::engine::{EngineState, Stack, StateWorkingSet};
-use nu_protocol::{report_error, Config};
-use nu_protocol::{ParseError, PipelineData, Spanned};
+use nu_protocol::{
+    engine::{EngineState, Stack, StateWorkingSet},
+    report_error, Config, ParseError, PipelineData, Spanned,
+};
 use nu_utils::{get_default_config, get_default_env};
-use std::fs::File;
-use std::io::Write;
-use std::panic::{catch_unwind, AssertUnwindSafe};
-use std::path::Path;
-use std::sync::Arc;
+use std::{
+    fs::File,
+    io::Write,
+    panic::{catch_unwind, AssertUnwindSafe},
+    path::Path,
+    sync::Arc,
+};
 
 pub(crate) const NUSHELL_FOLDER: &str = "nushell";
 const CONFIG_FILE: &str = "config.nu";

src/run.rs

@@ -7,8 +7,7 @@ use crate::{
 #[cfg(feature = "plugin")]
 use nu_cli::read_plugin_file;
 use nu_cli::{evaluate_commands, evaluate_file, evaluate_repl};
-use nu_protocol::eval_const::create_nu_constant;
-use nu_protocol::{PipelineData, Span, NU_VARIABLE_ID};
+use nu_protocol::{eval_const::create_nu_constant, PipelineData, Span, NU_VARIABLE_ID};
 use nu_utils::utils::perf;
 
 pub(crate) fn run_commands(

src/signals.rs

@@ -1,10 +1,9 @@
+use nu_protocol::engine::EngineState;
 use std::sync::{
     atomic::{AtomicBool, Ordering},
     Arc,
 };
 
-use nu_protocol::engine::EngineState;
-
 pub(crate) fn ctrlc_protection(engine_state: &mut EngineState, ctrlc: &Arc<AtomicBool>) {
     let handler_ctrlc = ctrlc.clone();
     let engine_state_ctrlc = ctrlc.clone();

src/test_bins.rs

@@ -1,9 +1,12 @@
 use nu_cmd_base::hook::{eval_env_change_hook, eval_hook};
 use nu_engine::eval_block;
 use nu_parser::parse;
-use nu_protocol::debugger::WithoutDebug;
-use nu_protocol::engine::{EngineState, Stack, StateWorkingSet};
-use nu_protocol::{cli_error::CliError, PipelineData, Value};
+use nu_protocol::{
+    cli_error::CliError,
+    debugger::WithoutDebug,
+    engine::{EngineState, Stack, StateWorkingSet},
+    PipelineData, Value,
+};
 use nu_std::load_standard_library;
 use std::io::{self, BufRead, Read, Write};