Uses `mw.trackSubscribe` to create an intermediary data handler
named `wikimedia.PageIssuesAB` which extends event-logging data
before passing it to the eventLogging through `wikimedia.event.PageIssues`.
Event hooks are placed where appropriate and the `CleanupOverlay`
class is extended to capture events from within the page issues
modal.
Additional changes:
* Merge two identical on click event handlers for
.edit-page, .edit-link elements
* change pageIssueParser.maxSeverity to accept an array of severity levels
instead of an array of pageIssues objects
Depends-On: Ic84e4a3286220407863167e0f57cef1b13a72964
Bug: T191532
Change-Id: I67fb6e448f6ecc97c89c1187e491ee05f7a312ef
