AssetManager: Cache a pre-filtered list of configurations

When we set the parameters for a ResTable, we can pre-filter which
resources match and only look at that smaller list when getting entries.
This helps A LOT with types that have many configurations, like strings
and all their various locales.

We must store the cached entries in a parallel data structure because parts
of the main Type object are shared with other ResTables, causing data races.

Bug:25499111
Change-Id: I63e37dcbd683fc9f1e7d0f3a6ed4c1c01e0fc575