Add FlightRecordWrapper for Safepower Agent

This change introduces a flight record wrapper class around a flight record request proto message.

The benefits are (1) it is clear what fields the flight record request is used, (2) the hashing and equality code is stored in the same spot (this change removes duplicate hashing logic) and (3) we can control how this is printed out--it is nicer to have flight records show on one line in logs.

PiperOrigin-RevId: 846910000
Change-Id: I50bac67d51492b8259f14a096880b7a41904b6e4