Split the CI tests (matrix, smoke, etc.) into discrete cluster providers

[rick-a-lane-ii]

Several of the CI tests are combining various cluster providers into one matrix. The issue with this is that this is not how it would be used in practice. Different parameters are going to be used with different providers, and the CI testing needs to ensure that extraneous parameters are not required in all cases.

i.e. we shouldn't require (or include) GKE parameters when creating Kubeception clusters

It would be better to just remove the provider matrix (confusingly and inconsistently called "distribution") altogether, and just have individual tests for different providers.

[rick-a-lane-ii]

Also change all instances of "distribution" => "provider", which should be minimal after the tests are redone.