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.

crates/nu-protocol/src/ast/expression.rs

@@ -1,11 +1,10 @@
-use std::sync::Arc;
-
+use crate::{
+    ast::{Argument, Block, Expr, ExternalArgument, ImportPattern, RecordItem},
+    engine::StateWorkingSet,
+    BlockId, DeclId, Signature, Span, Type, VarId, IN_VARIABLE_ID,
+};
 use serde::{Deserialize, Serialize};
-
-use super::{Argument, Block, Expr, ExternalArgument, RecordItem};
-use crate::ast::ImportPattern;
-use crate::DeclId;
-use crate::{engine::StateWorkingSet, BlockId, Signature, Span, Type, VarId, IN_VARIABLE_ID};
+use std::sync::Arc;
 
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct Expression {