Add -n flag to sort (formerly only available on sort-by) (#7293)

# Description

* `-n`, `--natural` flag from `sort-by` is now on the plain `sort`.
* The `-i`, `-n` and `-r` flags now work with single record sorting
(formerly they didn't)

# User-Facing Changes

See above.

# 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

@@ -75,6 +75,7 @@ mod semicolon;
 mod seq_char;
 mod shells;
 mod skip;
+mod sort;
 mod sort_by;
 mod source_env;
 mod split_by;