* Made DalamudAsset-to-something tables into arrays from dictionaries.
Number of items in the DalamudAsset enum aren't many, and the numbers
are small enough that implementing lookup tables as arrays aren't
wasting much memory space.
* Removed locking from asset accessors, while still guaranteeing that
the load operation happens only once per asset.
* ISharedImmediateTexture: made it not even access assets if textures
are available.
