Allow armaments to be enabled/disabled by upgrades.

Split from #6556, this integrates Armaments with the new upgrades system.  This will be useful for elite units and for upgrades such as the mammoth tank railguns in C&C3.

See https://github.com/pchote/OpenRA/commit/82ebf833cde46c6483caad3191f6bc509b6c3a19 for a testcase.