Optimize FilterApkAssets by caching config

ResTable_config of every ResTable_type is read from device every time
AssetManager::RebuildFilterList is invoked. For large APKs (like
framework-res.apk), this causes a large number of page faults
when accessing the config from disk. The configs are also used in the
slow path of AssetManager::FindEntryInternal, which makes it even
slower. Instead cache the config on the TypeSpec of its ApkAsset.

Bug: 177247024
Test: libandroidfw_tests
Change-Id: I66d507c4eeb2399f7558f3d9dfc53c157129ada0