Rewrite StackMap location handling to pre-compute the dwarf register

Rewrite StackMap location handling to pre-compute the dwarf register
numbers before emission.

This removes a dependency on being able to access TRI at the module
level and is similar to the DwarfExpression handling. I've modified
the debug support into print/dump routines that'll do the same dumping
but is now callable anywhere and if TRI isn't available will go ahead
and just print out raw register numbers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232821 91177308-0d34-0410-b5e6-96231b3b80d8