[llvm] [KeyInstr] Add bitcode support (PR #144102)

[Jeremy Morse via llvm-commits]

https://github.com/jmorse commented:

Looks good; do you have any size comparisons for bitcode files as a result of this? All the DILocations are bigger (regardless of KI mode), but on the other hand the debug-loc-again optimisation will avoid paying for that for every instruction.

https://github.com/llvm/llvm-project/pull/144102