Minor bug fixes and documentation cleanups: - display packages in CI builds to catch changes - stop compiler complaining about exec stacks in test cases - stop loongarch compiler complaining about rwx in test cases - improve docs on running TCG tests - remove old unneeded avocado test for memory callback testing - move test plugins into tcg testing dir - clean-up and move plugin documentation to emulation section - remove dead code from cache modelling plugin - add compatibility workaround for lockstep plugin - make some noise when building contrib plugins