[FR]: Promote -[FIRTrace cancel] to API

[jotai-coder]

Description

This post over in the Android SDK explains the need well -- an explicit means of discarding/invalidating a custom trace that should not be reported:
firebase/firebase-android-sdk#4866

API Proposal

-[FIRTrace cancel] -- or, if that has different semantics, -[FIRTrace invalidate]

Firebase Product(s)

Performance

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.