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-command/src/database/commands/into_sqlite.rs

@@ -1,15 +1,13 @@
 use crate::database::values::sqlite::{open_sqlite_db, values_to_sql};
+use nu_engine::command_prelude::*;
 
-use nu_engine::CallExt;
-use nu_protocol::ast::Call;
-use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{
-    Category, Example, IntoPipelineData, PipelineData, Record, ShellError, Signature, Span,
-    Spanned, SyntaxShape, Type, Value,
+use std::{
+    path::Path,
+    sync::{
+        atomic::{AtomicBool, Ordering},
+        Arc,
+    },
 };
-use std::path::Path;
-use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::Arc;
 
 pub const DEFAULT_TABLE_NAME: &str = "main";
 

crates/nu-command/src/database/commands/query_db.rs

@@ -1,14 +1,5 @@
-use nu_engine::CallExt;
-use nu_protocol::{
-    ast::Call,
-    engine::{Command, EngineState, Stack},
-    record, Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span,
-    Spanned, SyntaxShape, Type, Value,
-};
-
-use crate::database::values::sqlite::nu_value_to_params;
-
-use super::super::SQLiteDatabase;
+use crate::database::{values::sqlite::nu_value_to_params, SQLiteDatabase};
+use nu_engine::command_prelude::*;
 
 #[derive(Clone)]
 pub struct QueryDb;

crates/nu-command/src/database/commands/schema.rs

@@ -1,11 +1,8 @@
 use super::super::SQLiteDatabase;
 use crate::database::values::definitions::{db_row::DbRow, db_table::DbTable};
-use nu_protocol::{
-    ast::Call,
-    engine::{Command, EngineState, Stack},
-    record, Category, Example, PipelineData, Record, ShellError, Signature, Span, Type, Value,
-};
+use nu_engine::command_prelude::*;
 use rusqlite::Connection;
+
 #[derive(Clone)]
 pub struct SchemaDb;