[BOLT] Align BranchInfo and FuncBranchData in DataAggregator::recordTrace

`DataAggregator::recordTrace` serves two purposes:
  - Attaching LBR fallthrough ("trace") information to CFG (`getBranchInfo`),
    which eventually gets emitted as YAML profile.
  - Populating vector of offsets that gets added to `FuncBranchData`, which
    eventually gets emitted as fdata profile.

`recordTrace` is invoked from `getFallthroughsInTrace` which checks its return
status and passes on the collected vector of offsets to `doTrace`.

However, if a malformed trace is passed to `recordTrace` it might partially
attach the profile to CFG and exit with false, not propagating the vector of
offsets to `doTrace`. This leads to a difference between fdata and yaml profile
collected from the same binary and the same perf file.

(Skylake LBR errata might produce such malformed traces where the last entry
is duplicated, resulting in invalid fallthrough path between the last two
entries).

There are two ways to handle this mismatch: c...