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-parser/src/flatten.rs

@@ -515,6 +515,9 @@ pub fn flatten_pattern(match_pattern: &MatchPattern) -> Vec<(Span, FlatShape)> {
         Pattern::IgnoreValue => {
             output.push((match_pattern.span, FlatShape::Nothing));
         }
+        Pattern::IgnoreRest => {
+            output.push((match_pattern.span, FlatShape::Nothing));
+        }
         Pattern::List(items) => {
             if let Some(first) = items.first() {
                 if let Some(last) = items.last() {
@@ -559,6 +562,9 @@ pub fn flatten_pattern(match_pattern: &MatchPattern) -> Vec<(Span, FlatShape)> {
         Pattern::Variable(_) => {
             output.push((match_pattern.span, FlatShape::Variable));
         }
+        Pattern::Rest(_) => {
+            output.push((match_pattern.span, FlatShape::Variable));
+        }
         Pattern::Or(patterns) => {
             for pattern in patterns {
                 output.extend(flatten_pattern(pattern));