This allows commands/contributions to enable/disable themselves based matching against the list of custom editors

Fixes #91397

Renaming to match new API proposal

For #77131

Fix a small bug of JsonValidation

Allows the filtering of timeline sources from the Timeline view

The timeline.showView setting is on by default for insiders

Fixes #91317

Fixes #91105

UI:
Adds Refresh icon to view title
Adds "Load more" entry at the end of the list for paging

API:
Restructures api around cursors
Renames TimelineCursor to generic TimelineOptions for more flexibility
Adds paging object to Timeline for clearer paging usage
Changes cursors to be strings, and explicit before and after cursors
Allows limit to take a cursor, so we can reload current data set
Clarifies id and fallback to timestamp
Adds reset flag to TimelineChangeEvent for providers to reset caching

Git provider:
Orders and returns commit date as the timestamp
Supports limit of a cursor (using rev-list --count)
Stops returning working/index changes when paging
Forcably resets cached data when changes are detected (naive for now)