Modernize Python typing across the codebase

Automated via ruff UP006, UP007, UP035, UP045 rules (target: py311):

- Replace `typing.List`, `Dict`, `Tuple`, `Set`, `FrozenSet`, `Type`
  with their built-in equivalents (`list`, `dict`, `tuple`, etc.)
- Replace `typing.Optional[X]` with `X | None`
- Replace `typing.Union[X, Y]` with `X | Y`
- Move `Mapping`, `Sequence`, `Callable`, `Awaitable`,
  `MutableMapping`, `MutableSequence`, `Iterator`, `AsyncIterator`,
  `AsyncGenerator` imports from `typing` to `collections.abc`
- Remove now-unused `typing` imports
- Add `from __future__ import annotations` to 5 files that use
  forward-reference strings in `X | "Y"` annotations

scripts/evals/run-release-evals.py

@@ -7,7 +7,7 @@
 import argparse
 import asyncio
 import sys
-from datetime import datetime, timezone
+from datetime import UTC, datetime, timezone
 from pathlib import Path
 
 from dotenv import load_dotenv
@@ -41,7 +41,7 @@ EVAL_WEATHER_AND_RESTAURANT = EvalConfig(
 
 EVAL_ONLINE_SEARCH = EvalConfig(
     prompt="What's the current date in UTC?",
-    eval=f"Current date in UTC is {datetime.now(timezone.utc).strftime('%A, %B %d, %Y')}.",
+    eval=f"Current date in UTC is {datetime.now(UTC).strftime('%A, %B %d, %Y')}.",
 )
 
 EVAL_SWITCH_LANGUAGE = EvalConfig(