Rename ruff_python crate to ruff_python_stdlib (#3354)

In hindsight, `ruff_python` is too general. A good giveaway is that it's actually a prefix of some other crates. The intent of this crate is to reimplement pieces of the Python standard library and CPython itself, so `ruff_python_stdlib` feels appropriate.

crates/ruff_python_stdlib/src/keyword.rs

@@ -0,0 +1,7 @@
+// See: https://github.com/python/cpython/blob/9d692841691590c25e6cf5b2250a594d3bf54825/Lib/keyword.py#L18
+pub const KWLIST: [&str; 35] = [
+    "False", "None", "True", "and", "as", "assert", "async", "await", "break", "class", "continue",
+    "def", "del", "elif", "else", "except", "finally", "for", "from", "global", "if", "import",
+    "in", "is", "lambda", "nonlocal", "not", "or", "pass", "raise", "return", "try", "while",
+    "with", "yield",
+];