Reduce cost of WindowTokenClient config change

The SizeConfigurationBuckets was used to avoid activity relaunch
by insignificant configuration change. Because WindowTokenClient
doesn't have relaunch operation, it is unnecessary to use it.
Especially Resources#getSizeConfigurations() is a heavy invocation,
which may create hundreds of temporal Configuration when calling it
in system server.

Also fix leakage of SystemUiContext if it is detached, e.g. the
associated display is removed.

Bug: 207620458
Test: atest WindowContextControllerTest
Change-Id: I8388a2ab25f3deed2e29eb5636c4b2130f4f1b87