Structure test: Add autoload.php order check

Structure test: Add autoload.php order check

If a class is added manually to the autoload.php another run of
the maintenance script will probably add unnecessary noise to
another change. The added structure test checks, if the output of
the maintenance script equals to the contents of the commited
autoload.php.

Bug: T121921
Change-Id: I3a426b92892f4c00cab33a13f6a717751120367c