[CSSPGO] Allow the use of debug-info-for-profiling and pseudo-probe-for-profiling together

Previoulsy debug-info-for-profiling and pseudo-probe-for-profiling are mutual exclusive because they compete the dwarf discrimnator for callsites on the IR. This changes allows to use the two switches together. The side effect is that callsite discriminators will be taken by pseudo probe, while discriminators for other instructions are still available for AutoFDO use. This is less than ideal, however, it still allows us a chance to smoothly transition from AutoFDO to CSSPGO, by collecting both profiles from a CSSPGO binary.

Reviewed By: wenlei, wmi

Differential Revision: https://reviews.llvm.org/D107876