Submit task to queue to sync ProtoLog stop

Instead of stopping and re-creating the executor everytime we can just rely on the FIFO nature of the SingleThreadExecutor to wait for all logs traced up to the onStop call to be flushed

Bug: 416468346
Bug: 410517697
Flag: EXEMPT minor tracing change
Test: atest com.android.internal.protolog.ProcessedPerfettoProtoLogImplTest
Change-Id: Ibc1373daa90bf57dcda53720c2cd1242fec28c9d