Transcribe data model update

[akashuc]

Issue #:

Description of changes: Update transcribe data model on CHIME-JS-SDK. The changes include introducing PII entities and stabilization factor. This change also include adding fields to the protobuf model and adding decoding logic for the entity received.

Testing:

Can these tested using a demo application? Please provide reproducible step-by-step instructions.
Yes MeetingV2 can be used to test this changes as well regression testing. The changes have been tested in gamma using the demo app.

Regression can be performed on the changes:

1. Use meetingV2 demo app
2. Start and join the meeting
3. Enable Live Transcription
4. Transcript should start coming as earlier.

Checklist:

1. Have you successfully run npm run build:release locally? yes

2. Do you add, modify, or delete public API definitions? If yes, has that been reviewed and approved? no

3. Do you change the wire protocol, e.g. the request method? If yes, has that been reviewed and approved?

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[haifengx]

lgtm

[richnew10]

This needs some thought to be given to the experience of a developer encountering this for the first time. Both developer docs (via block comments and included examples) and TypeScript help need attention.