Recommit: DebugInfo: Check DW_OP_convert in loclists with Split DWARF

Originally committed in: 552a8fe1
            Reverted in: f75301d1

Reverted because it was running llc directly (rather than %llc_dwarf)
which uses COFF files on Windows which LLVM doesn't support all DWARF
features in.

This functionality isn't fully working, but sets up the testing for a
follow-on patch that demonstrates and fixes the brokenness related to
DWO ID hashing this construct.