Implements:
* Gadget definition content and content handler
* Basic validation for gadget definition content
* GadgetDefinitionNamespace implementation of GadgetRepo
* DataUpdates upon editing/deletion of Gadget definition pages
* EditFilterMerged hook for improved error messages
* 'GadgetsRepoClass' option to switch GadgetRepo implementation used
* Lazy-load the GadgetResourceLoaderModule class so we don't need to
load each individual gadget object unless its needed
Note that Special:Gadgets's export feature intentionally doesn't work
yet, and will be fixed in a follow up patch.
Bug: T106177
Change-Id: Ib11db5fb0f7b46793bfa956cf1367f1dc1059b1c
GadgetRepo is an abstract class based off of the implementation in the
RL2 branch.
It is a singleton that provides basic methods to construct and interact
with Gadget objects.
The MediaWikiGadgetsDefinition class is an implementation of GadgetsRepo
that parses the "MediaWiki:Gadgets-definition" page for gadget
definitions.
Tests were left in place to demonstrate that no functional changes have
been made aside from relocation of code. Some tests should be moved to
separate files in the future.
Bug: T106176
Change-Id: I3e802889f6f495783f4dbac65c2a8cefa824a778
