Fix ConcurrentModificationException on WindowToken

Because there can be multiple different UI threads for different
View windows, the corresponding configuration changed callback can be
triggered in different threads.

Add lock to make it thread-safe.

Fix: 335967960
Test: Refactor pass existing tests
Flag: com.android.window.flags.window_token_config_thread_safe
Change-Id: I504731bf60f029010ebd370bb2b2e99199998f2f