Migrate scap-1, scap-2, & sync-common from wikimedia-task-appserver

This change migrates three scripts from wikimedia-task-appserver:

- scap-1 (at ff2d5a7fe3 / Gerrit change Iae053bd09)
- scap-2 (at ea5a1a889a / Gerrit change I64d6246ed)
- sync-common (at 66fc5c65cc /
    <http://www.mediawiki.org/wiki/Special:Code/MediaWiki/91703>)

Managing these scripts in a single repository will make it easier to update
their content and keep them in sync.

Somewhat awkwardly, the resources representing these scripts must be declared
in class mediawiki::sync, rather than misc::deployment::scap_scripts. This is
because the scripts must be present on both the scap source server and all scap
targets.

Because scap already depends on sync-common, the cross-module dependency is
already in place: misc::deployment::scap_scripts requires
misc::deployment::common_scripts, which in turn requires mediawiki.

The corresponding change to wikimedia-task-appserver to remove these scripts is
I047f37b0a.

I am unfortunately not able to test this thoroughly.

RT: 3276
Bug: 40025
Change-Id: I33d93347f811906f37d503039af7035d122938b9