Revert "Revert "Refactor OperationName to use virtual tables for dispatch (NFC)""

Revert "Revert "Refactor OperationName to use virtual tables for dispatch (NFC)""

This streamlines the implementation and makes it so that the virtual
tables are in the binary instead of dynamically assembled during initialization.
The dynamic allocation size of op registration is also smaller with this
change.

This reverts commit 7bf1e441da6b59a25495fde8e34939f93548cc6d
and re-introduce e055aad5ffb348472c65dfcbede85f39efe8f906
after fixing the windows crash by making ParseAssemblyFn a
unique_function again

Differential Revision: https://reviews.llvm.org/D141492