[BOLT] Better match LTO functions profile.

Summary:
* Improve profile matching for LTO binaries that don't match 100%.
* Fix profile matching for '.LTHUNK*' functions.
* Add external outgoing branches (calls) for profile validation.

There's an improvement for 100% match profile and for stale LTO
profile. However, we are still not fully closing the gap with
stale profile when LTO is enabled.

(NOTE: I haven't updated all test cases yet)

(cherry picked from FBD5529293)