Customize: changeset_uuid query param doesn't get stripped at initial save of starter content

[westonruter]

A changeset_uuid query parameter is added to the window's location via replaceState after a changeset is created and should remain until it is published. Upon publishing, the parameter should be removed because published changesets are frozen and cannot be opened in the customizer. When a changeset is published, a new changeset UUID is generated and is then supplied the next time changes are made.

When loading up a fresh_site and saving the starter content, the initial publishing is causing the next UUID to be supplied into changeset_uuid query param unexpectedly when it should be left empty.

[dlh]

39081.0.diff​ works as expected for me.

[westonruter]

In 39504:

Customize: Ensure changeset_uuid query param is removed from the customize.php window's location once a changeset has been published (committed) with starter content.

Props westonruter, dlh for testing.
See #30937.
Fixes #39081.

[westonruter]

In 39505:

Customize: Ensure changeset_uuid query param is removed from the customize.php window's location once a changeset has been published (committed) with starter content.

Props westonruter, dlh for testing.
Merges [39504] onto 4.7 branch.
Fixes #39081 for 4.7.