Defer deleting a http cache

Symptom:
StatementService was crashed due to the exception;
"java.lang.IllegalStateException: cache is closed"

Root cause:
The http cache is deleted at DirectStatementService#onDestroy
in main thread. If a worker thread is still alive and it tries to
access the cache, it fails with IllegalStateException.

Solution:
The request of deleting a cache was moved from the main thread to
worker. Now, the cache can be deleted safely.

Cherrypick from AOSP master.

Bug: 73911877
Test: manual
Change-Id: I61f4e62b00e35f4a272ef983758e61ef3bf2d180
Merged-In: I61f4e62b00e35f4a272ef983758e61ef3bf2d180