enable tests based on CPU resource accounting

[dgrove-oss]

1. Measure cluster capacity before starting test suite.
2. Express CPU resource requests in test cases in terms of fractions of cluster capacity
3. Start consolidating deployment configurations in aw_fixtures.
4. Misc small test cleanups.

To validate that the tests are now not sensitive to cluster size I tested by limiting Rancher Desktop on my laptop to 2, 4, and 8 CPUs and observing tests ran correctly on all three sizes of kind clusters.

[dgrove-oss]

Might be easier to review commit by commit since 4d0b961 just moved functions around without changing them.

[tardieu]

LGTM. As discussed orally, it would be good to share the cluster capacity computation between the controller and the test code in another PR.