[memprof] Undrift MemProfRecord (#120138)
This patch undrifts source locations in MemProfRecord before readMemprof
starts the matching process.
The thoery of operation is as follows:
1. Collect the lists of direct calls, one from the IR and the other
from the profile.
2. Compute the correspondence (called undrift map in the patch)
between the two lists with longestCommonSequence.
3. Apply the undrift map just before readMemprof consumes
MemProfRecord.
The new function gated by a flag that is off by default.
