🐛 Remove requirement to specify CAPIProvider secret

[Danil-Grigorev]

What this PR does / why we need it:
This change improves the process of CAPIProvider creation. Users don’t need to specify spec.configSecret at all times, in order to get default set of enabled features, such as ClusterClasses or MachinePools, + provider specific features.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #787

Special notes for your reviewer:

Checklist:

• squashed commits into logical changes
• includes documentation
• adds unit tests
• adds or updates e2e tests

[salasberryfin]

Thanks @Danil-Grigorev. If using this "minimal" CAPIProvider yaml and, for example, wanting to enable Cluster Classes, is it not required to pass the CUSTER_TOPOLOGY environment variable to the provider? This question would apply to any other feature that used to be enabled via variables before this change.

[Danil-Grigorev]

@salasberryfin Yes, there is a test case for that also https://github.com/rancher/turtles/pull/788/files#diff-4f7dd9c7662f229992f65de2f22cd082cb79ba691af9062fed41ae5e472180c7R97