fix(anthropic): replace retired model IDs in tests and docstrings (#35365)

## Summary

- Replace `claude-3-5-haiku-20241022` and `claude-3-7-sonnet-20250219`
with `claude-haiku-4-5-20251001` and `claude-sonnet-4-5-20250929`
respectively
- Both models were retired by Anthropic on February 19, 2026, causing
all anthropic integration tests to fail
- Updates integration tests, a unit test, and docstring examples in
`langchain-core`

See:
https://platform.claude.com/docs/en/docs/resources/model-deprecations

libs/partners/anthropic/tests/unit_tests/test_standard.py

@@ -48,7 +48,7 @@ def test_init_time_with_client(benchmark: BenchmarkFixture) -> None:
 
     def _init_in_loop_with_clients() -> None:
         for _ in range(10):
-            llm = ChatAnthropic(model="claude-3-5-haiku-20241022")
+            llm = ChatAnthropic(model="claude-haiku-4-5-20251001")
             _ = llm._client
             _ = llm._async_client