Add aiobotocore support for async AWS SDK recording/playback

[ningsuhen-lyra]

Summary

This PR adds support for recording and playing back HTTP requests made via aiobotocore, the async version of boto3/botocore.

aiobotocore uses aiohttp internally but wraps responses in its own AioAWSResponse class. This implementation patches aiobotocore.httpsession.AIOHTTPSession.send to intercept requests and either:

• Play back recorded responses from cassettes
• Record real responses during recording mode
• Raise CannotOverwriteExistingCassetteException when write-protected

Changes

• New file: vcr/stubs/aiobotocore_stubs.py - Mock response classes (MockAioHTTPResponse, MockAioAWSResponse) and request/response handling
• Modified: vcr/patch.py - Added aiobotocore patching to CassettePatcherBuilder
• New file: tests/integration/test_aiobotocore.py - Integration tests for aiobotocore support

Implementation Notes

• The mock response classes implement the interfaces expected by botocore's response parsing:

  • raw_headers property returning [(bytes, bytes), ...]
  • async read() method for body content
  • status_code, headers, and url attributes

• aiobotocore has a circular import issue when importing aiobotocore.httpsession directly, so we import aiobotocore.session first to resolve the dependency graph

Test Plan

• Basic cassette context manager works with aiobotocore
• Playback from pre-recorded cassettes works correctly
• Response body, headers, and status code are properly serialized/deserialized
• Existing aiohttp tests still pass (no regressions)
• Existing boto3 tests still pass (no regressions)

Related Issues

This enables testing of async AWS services using aiobotocore without making real network calls, similar to how vcrpy already supports boto3 (sync) and aiohttp.