Make seq return a ListStream where possible (#7367)

# Description

Title.

# User-Facing Changes

Faster seq that works better with functions that take in `ListStream`s.

# 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

# 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-command/tests/commands/mod.rs

@@ -72,6 +72,7 @@ mod run_external;
 mod save;
 mod select;
 mod semicolon;
+mod seq;
 mod seq_char;
 mod shells;
 mod skip;