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.

Bug:25499111
Change-Id: Ie6894c44bc67e16a10dbe028c8f3e119e5c29ac7