Sessions were being erroneously cached and reused across different asyncio event loops, causing "Event loop is closed" in environments with transient loops. This updates the session caching to be loop-aware: before reusing a cached session, check that the stored loop matches the current loop. Also, if session is disconnected and loops do not match, discard the cached entry without calling aclose().
Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 868380746
Kathy WuandCopybara-Service
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