anthropic[major]: support python 3.13 (#27916)

Last week Anthropic released version 0.39.0 of its python sdk, which
enabled support for Python 3.13. This release deleted a legacy
`client.count_tokens` method, which we currently access during init of
the `Anthropic` LLM. Anthropic has replaced this functionality with the
[client.beta.messages.count_tokens()
API](https://github.com/anthropics/anthropic-sdk-python/pull/726).

To enable support for `anthropic >= 0.39.0` and Python 3.13, here we
drop support for the legacy token counting method, and add support for
the new method via `ChatAnthropic.get_num_tokens_from_messages`.

To fully support the token counting API, we update the signature of
`get_num_tokens_from_message` to accept tools everywhere.

---------

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>

.github/scripts/check_diff.py

@@ -37,7 +37,6 @@ IGNORED_PARTNERS = [
 PY_312_MAX_PACKAGES = [
     f"libs/partners/{integration}"
     for integration in [
-        "anthropic",
         "chroma",
         "couchbase",
         "huggingface",