Defer endpoint session cleanup on openSession HAL errors

This change defers the cleanup of endpoint session resources to an
executor when an exception occurs during the HAL `openEndpointSession`
call. Instead of synchronously cleaning up and re-throwing, the session
is closed asynchronously with an appropriate reason. The executor is
also renamed to reflect its broader use.

Bug: 443346395
Flag: EXEMPT BUGFIX
Test: Presubmit
Change-Id: I43c532b1c4970335f71acca217f6309f01de2e5a