fix: keep responses for oversized JSON integers

[he-yufeng]

Summary

• catch ValueError in the response-schema parsing paths that already ignore invalid JSON
• keep the GenerateContentResponse object available when Python rejects a runaway integer literal via int_max_str_digits
• add a regression for both response_schema and response_json_schema

Fixes #2542.

Verification

$env:PYTHONPATH='.'; $env:GOOGLE_GENAI_REPLAYS_DIRECTORY="$env:TEMP\google-genai-replays"; python -m pytest google\genai\tests\models\test_generate_content.py -k oversized_json_integer -q
python -m py_compile google\genai\types.py google\genai\tests\models\test_generate_content.py
python -m ruff check --select E9,F63,F7,F82 google\genai\types.py google\genai\tests\models\test_generate_content.py
git diff --check

[he-yufeng]

Rebased this branch onto current main and re-ran the targeted local checks.

Verified:

• GOOGLE_GENAI_REPLAYS_DIRECTORY=$TEMP/genai-replays-empty python -m pytest google/genai/tests/models/test_generate_content.py -q -k "oversized_json_integer" -> 4 passed
• python -m py_compile google/genai/types.py google/genai/tests/models/test_generate_content.py
• git diff --check upstream/main..HEAD

I did not reformat the whole files for this small fix. ruff check / ruff format --check still touch pre-existing unrelated lines in these generated/large files.