Refactoring and adding TOS check before transcribing

This cl just adds a check before starting a transcription job
to verify that the user has accepted the appropriate TOS. Its
a rather big cl just because it had to expose some TOS acceptance
details that were previously encapsulated in the VoicemailTosMessageCreator.

Bug: 69267260
Test: manual and unit tests
PiperOrigin-RevId: 176132370
Change-Id: Ic28fb197a07f9df7a9b5f1729c84566cba0890fc