Migrate kwin animation speed to kdeglobals

Test Plan:
Tested output piping test lines into the script with different settings
Removed from my kdeglobals
Invoked script. New value appeared

(note that if you manually test multiple times locally you have to
cleanup the $version info from
both kdeglobals and kwinrc or the migration will be skipped)

Reviewers: zzag

Reviewed By: zzag

Subscribers: zzag, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D24084