Rename ruff_cli crate to ruff (#9557)

## Summary

Long ago, we had a single `ruff` crate. We started to break that up, and
at some point, we wanted to separate the CLI from the core library. So
we created `ruff_cli`, which created a `ruff` binary. Later, the `ruff`
crate was renamed to `ruff_linter` and further broken up into additional
crates.

(This is all from memory -- I didn't bother to look through the history
to ensure that this is 100% correct :))

Now that `ruff` no longer exists, this PR renames `ruff_cli` to `ruff`.
The primary benefit is that the binary target and the crate name are now
the same, which helps with downstream tooling like `cargo-dist`, and
also removes some complexity from the crate and `Cargo.toml` itself.

## Test Plan

- Ran `rm -rf target/release`.
- Ran `cargo build --release`.
- Verified that `./target/release/ruff` was created.

crates/ruff_linter/src/rule_selector.rs

@@ -108,7 +108,7 @@ pub(crate) fn is_single_rule_selector(prefix: &RuleCodePrefix) -> bool {
 pub enum ParseError {
     #[error("Unknown rule selector: `{0}`")]
     // TODO(martin): tell the user how to discover rule codes via the CLI once such a command is
-    // implemented (but that should of course be done only in ruff_cli and not here)
+    // implemented (but that should of course be done only in ruff and not here)
     Unknown(String),
 }