Add rest and ignore-rest patterns (#8681)

# Description

Adds two more patterns when working with lists:

```
[1, ..$remainder]
```
and
```
[1, ..]
```
The first one collects the remaining items and assigns them into the
variable. The second one ignores any remaining values.

# User-Facing Changes

Adds more capability to list pattern matching.

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass
- `cargo run -- crates/nu-utils/standard_library/tests.nu` to run the
tests for the standard library

> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-protocol/src/engine/pattern_match.rs

@@ -18,6 +18,8 @@ impl Matcher for Pattern {
         match self {
             Pattern::Garbage => false,
             Pattern::IgnoreValue => true,
+            Pattern::IgnoreRest => false, // `..` and `..$foo` only match in specific contexts
+            Pattern::Rest(_) => false,    // so we return false here and handle them elsewhere
             Pattern::Record(field_patterns) => match value {
                 Value::Record { cols, vals, .. } => {
                     'top: for field_pattern in field_patterns {
@@ -46,17 +48,47 @@ impl Matcher for Pattern {
             Pattern::List(items) => match &value {
                 Value::List { vals, .. } => {
                     if items.len() > vals.len() {
-                        // We need more items in our pattern than are available in the Value
-                        return false;
+                        // The only we we allow this is to have a rest pattern in the n+1 position
+                        if items.len() == (vals.len() + 1) {
+                            match &items[vals.len()].pattern {
+                                Pattern::IgnoreRest => {}
+                                Pattern::Rest(var_id) => {
+                                    matches.push((*var_id, Value::nothing(items[vals.len()].span)))
+                                }
+                                _ => {
+                                    // There is a pattern which can't skip missing values, so we fail
+                                    return false;
+                                }
+                            }
+                        } else {
+                            // There are patterns that can't be matches, so we fail
+                            return false;
+                        }
                     }
-
                     for (val_idx, val) in vals.iter().enumerate() {
                         // We require that the pattern and the value have the same number of items, or the pattern does not match
                         // The only exception is if the pattern includes a `..` pattern
-
                         if let Some(pattern) = items.get(val_idx) {
-                            if !pattern.match_value(val, matches) {
-                                return false;
+                            match &pattern.pattern {
+                                Pattern::IgnoreRest => {
+                                    break;
+                                }
+                                Pattern::Rest(var_id) => {
+                                    let rest_vals = vals[val_idx..].to_vec();
+                                    matches.push((
+                                        *var_id,
+                                        Value::List {
+                                            vals: rest_vals,
+                                            span: pattern.span,
+                                        },
+                                    ));
+                                    break;
+                                }
+                                _ => {
+                                    if !pattern.match_value(val, matches) {
+                                        return false;
+                                    }
+                                }
                             }
                         } else {
                             return false;