[BOLT] Fix branch info stats after SCTC

Summary:
SCTC was incorrectly swapping BranchInfo when reversing the branch condition.  This was wrong because when we remove the successor BB later, it removes the BranchInfo for that BB.  In this case the successor would be the BB with the stats we had just swapped.

Instead leave BranchInfo as it is and read the branch count from the false or true branch depending on whether we reverse or replace the branch, respectively.  The call to removeSuccessor later will remove the unused BranchInfo we no longer care about.

(cherry picked from FBD6876799)