This commits removes TableGens reliance on managed static global record state
by moving the RecordContext into the RecordKeeper. The RecordKeeper is now
treated similarly to a (LLVM|MLIR|etc)Context object and is passed to static
construction functions. This is an important step forward in removing TableGens
reliance on global state, and in a followup will allow for users that parse tablegen
to parse multiple tablegen files without worrying about Record lifetime.
Differential Revision: https://reviews.llvm.org/D125276
Since now we are able to handle both fixed length & variable
length instructions.
Reviewed By: myhsu
Differential Revision: https://reviews.llvm.org/D123451