Add support for EC2 Placement Host Resource Group Arn parameter [JENKINS-66901]

[joneskoo]

Implemented JENKINS-66901 parameter to set host resource group, to be used to dynamically allocate and release dedicated hosts, in particular for Mac instances.

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I have manually tested the change works to successfully launch Mac instances, with or without host resource group set. I was not able to run the tests in my local environment and not sure how this could be meaningfully unit tested.

This is authored by me and copyright my employer WithSecure Corporation and I have permission to contribute it to the project under original license.

[joneskoo]

Ok so the tests broke, not a surprise since I wasn't able to get them to run even without any changes. I'll see if I figure out the problem and fix the tests.

[joneskoo]

See https://issues.jenkins.io/browse/JENKINS-66901 . There is a way to use Host Resource Group and License Manager without changes to EC2 plugin.

Otherwise would need to also add license configuration for License Manager, host resource group is not sufficient to launch.