Switch to ConcurrentHashMap for CompatConfig

Use ConcurrentHashMap instead of a SparseLongArray guarded by a
reentrant readwrite lock to make CompatConfig.isChangeEnabled as fast as
possible.

Test: atest CompatConfigTest
Bug: 197712476
Bug: 191398285
Change-Id: I498c439baf3e060ec7feb68ed581ca680e2ebcad