Also adds `timeline.pageSize` to explicitly choose a page size

Separates the tree rendering from the data model cache
Fixes many issues and simplifies the code

timeline contrinbtuion: do not call localize on localized strings. Aslo use fixes string for localization keys

Adds follow/unfollow actions to the timeline view
Reworks timeline view commands

Allows the filtering of timeline sources from the Timeline view

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)

Adds contributable commands to timeline items
Adds right-aligned timestamp to timeline items
Adds Open Changes to Git timeline items
Adds Copy Commit ID to Git timeline items
Adds Copy Commit Message to Git timeline items

For #81574

Based on https://stackoverflow.com/questions/59384319/typescript-get-typeof-generic-constructor