[DFSan] Add dfsan-combine-taint-lookup-table option as work around for

false negatives when dfsan-combine-pointer-labels-on-load=0 and
dfsan-combine-offset-labels-on-gep=0 miss data flows through lookup tables.

Example case:
https://github.com/abseil/abseil-cpp/blob/628a2825f8dc0219964886e7cc3f7f519e3bd950/absl/strings/ascii.h#L182

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D122787