[BOLT] Support for non-LBR profile in YAML

Summary:
Expanded YAML profile format to support different kinds of profile
including LBR and non-LBR (and memevents in the future).

The profile now starts with a header that includes the profile
description. "profile-flags" field includes either "lbr" or "sample",
but not both at the same time. It could also include "memevent" in
addition to other flags.

For now, the only way to generate non-LBR YAML profile is through
conversion. Once task is done, it should be possible to use
perf2bolt for it.

(cherry picked from FBD7595693)