Make XDM changes for all Alpha temporary fields

## What are the schemas that are affected by the issue

* media.schema.json
* time-series.schema.json
* rating.schema.json

## What are examples of products that are impacted by the issue

* Adobe Media Analytics
Internal JIRA issues: https://jira.corp.adobe.com/browse/VA-4673 + https://jira.corp.adobe.com/browse/VA-4663 + https://jira.corp.adobe.com/browse/VA-4661 + https://jira.corp.adobe.com/browse/VA-4999

High-level changes:
* support for playhead parameter https://experienceleague.adobe.com/docs/media-analytics/using/media-collection-api/mc-api-ref/mc-api-sessions-req.html?lang=en
* support for media types for eventType enum in time-series schema
* correct the regex of /media/mediaTimed/primaryAssetViewDetails/videoSegment to ^[[0-9]+-[0-9]+]$
* make RatingSourceLink optional since we don't ask it as input from our clients
* integrate multiple player state tracking for ee integration by adding statesStart and statesEnd

Start with media.schema.json, time-series.schema.json, and rating.schema.json, then compare their current definitions with the listed Adobe Media Analytics requirements and linked documentation. Confirm that all five requested changes are represented across the affected schemas, including the playhead, media types, videoSegment regex, optional RatingSourceLink, and player state fields.

Written by the indexing model from the issue text.