Compute unique layer name in with sequence

Remove 'getUniqueLayerName' so we could remove stack lock from
'createLayer'.

Bug: 202621651
Test: atest libsurfaceflinger_unittest
Test: atest SurfaceFlinger_test
Change-Id: If5f4386b6da99bd540231b0c197c59a5823d7d4a
4 files changed