resources: Move more various single-file mediawiki.* modules to src/

resources: Move more various single-file mediawiki.* modules to src/

* Reduce clutter in src/mediawiki/.
* Make these files and modules easier to discover and associate.

Follows-up I677edac3b5e, which only moved simple cases where no
related modules existed.

This commit also moves files for modules that have some related
multi-file modules. As well as files that previously did not
strictly have their path match directly to their module name.

For example:
- 'mediawiki.checkboxtoggle.css' to 'mediawiki.checkboxtoggle.styles.css',
  because its module name is 'mediawiki.checkboxtoggle.styles'.
- 'mediawiki/page/gallery-slideshow.js' to 'mediawiki.page.gallery.slideshow.js',
  because its module name uses a dot, not a dash.
- 'mediawiki/page/watch.js' to 'mediawiki.page.watch.ajax.js',
  because its module name also includes 'ajax'. This also makes it matches
  the way "mediawiki.page.patrol.ajax" files were already named.

Ideas for later:
- Consider merging 'mediawiki.ForeignApi' and 'mediawiki.ForeignApi.core.'.
- Consider merging 'mediawiki.page.ready' and 'mediawiki.page.startup'.

Bug: T193826
Change-Id: I9564b05df305b7d217c9a03b80ce92476279e5c8