[mlir] Refactor StorageUniquer to require registration of possible storage types

This allows for bucketing the different possible storage types, with each bucket having its own allocator/mutex/instance map. This greatly reduces the amount of lock contention when multi-threading is enabled. On some non-trivial .mlir modules (>300K operations), this led to a compile time decrease of a single conversion pass by around half a second(>25%).

Differential Revision: https://reviews.llvm.org/D82596