[res] Stop using try_emplace for hash maps

1. Turns out libcxx's try_emplace() on unordered containers is
slower than even find + insert pair. Revert the 'optimization'
back to get the performance back

2. Fix the cache invalidation in AssetManager to keep the caches
coherent.

Bug: 282264161
Test: build + UTs + boot
Change-Id: I823215beb863c0ffaf703c70bb4358c331da8251