Rename ruff_python_whitespace to ruff_python_trivia (#5886)

## Summary

This crate now contains utilities for dealing with trivia more broadly:
whitespace, newlines, "simple" trivia lexing, etc. So renaming it to
reflect its increased responsibilities.

To avoid conflicts, I've also renamed `Token` and `TokenKind` to
`SimpleToken` and `SimpleTokenKind`.

crates/ruff_textwrap/src/lib.rs

@@ -4,7 +4,7 @@
 use std::borrow::Cow;
 use std::cmp;
 
-use ruff_python_whitespace::{PythonWhitespace, UniversalNewlines};
+use ruff_python_trivia::{PythonWhitespace, UniversalNewlines};
 
 /// Indent each line by the given prefix.
 ///