Decomission: Reduce number of AWS machines that we use

[sxa]

We are looking to reduce the number of machines we host with AWS in order to keep costs down. Similar to #1781 we can move some of these onto other providers and/or docker containers. Some of them have been taken offline for the last couple of weeks to see if we have adequate capacity without the AWS systems. Here is the list

System	Size	Recommending removal?
git-hg mirror	small	No (Only other git-hg was on GoDaddy)
docker-x64-1 and -2	2 core, 4/8 Gb	Yes (subject to multiarch job not failing elsewhere) and moving DockerfileCheck
test-rhel8-x64	4core/16GB	No - don't have other RHEL8/x64 boxes
test-ubuntu20-x64	4 core/16GB)	Yes - we have others in docker on 20.04 hosts)
test-rhel-aarch64-1 to 6		Yes (maybe keep -1 for now)
test-ubuntu1804-aarch64		Undecided :-)
test-win2019-x64-1 and -2	4 core, 16GB)	Retain 1 as no other Win2019 systems
TRSS	8 core, 16GB	Yes

Plus a few other test/temp systems that are no longer needed.

I expect to do this in the next week. Certainly a few of these have been offline for a while, and so can be removed independently of the release cycle next week. Anything still live should wait until the release is out.

[sxa]

Decomissioned the following:

• test-rhel-aarch64-2 through 6
• docker-aws-ubuntu1604-x64-2
• test-aws-win2019-x64-2
• test-aws-ubuntu2004-x64-1

I'm going to keep test-ubuntu1804-aarch64 in place for now as we don't have another system running that level outside docker, but will likely replace with something at the colo setup once available.