Bugfix: review_session_active triggered by the frame_change_update handler

Description of change

• renamed review_session_started into review_session_active to be more consistent.
• Added a keeper for review_session_active to avoid the change due to frame_change_update and ensure this is triggered only by a user action.

How to test it

• Load timeline, link reviews, the review session is not started by default.

Checklist

Please check if your MR fulfills the following requirements:

• Unit tests have been added, if needed
• Documentation have been updated, if needed
• Build was run locally and any changes were pushed
• Lint has passed locally without error
• Package.py have been updated, if needed
• CHANGELOG.md have been updated, if needed
• Version numer has been tagged, if needed

FYI: @awesome_dev_too