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_python_formatter/src/comments/format.rs

@@ -3,7 +3,7 @@ use rustpython_parser::ast::Ranged;
 
 use ruff_formatter::{format_args, write, FormatError, SourceCode};
 use ruff_python_ast::node::{AnyNodeRef, AstNode};
-use ruff_python_whitespace::{lines_after, lines_before, skip_trailing_trivia};
+use ruff_python_trivia::{lines_after, lines_before, skip_trailing_trivia};
 
 use crate::comments::SourceComment;
 use crate::context::NodeLevel;