AudioFlinger: Refactor SyncEvent

Extract SyncEvent code as is to separate file.

Test: atest MediaSyncEventTest
Bug: 283021652
Merged-In: I2212cdc52513f49b08e0383f26548f6dbda4741c
Change-Id: I2212cdc52513f49b08e0383f26548f6dbda4741c
3 files changed