What this PR does / why we need it:

This change allows to use mounted clusterctl-config.yaml file to override provider images.

apiVersion: v1
data:
  clusterctl.yaml: |
    images:
      control-plane-rke2:
        repository: myorg.io/local-repo
        tag: v9.9.9
      bootstrap-rke2:
        repository: myorg.io/local-repo
        tag: v9.8.9

results in:
image: http://myorg.io/local-repo/cluster-api-provider-rke2-controlplane:v9.9.9
and
image: http://myorg.io/local-repo/cluster-api-provider-rke2-bootstrap:v9.8.9

for rke2 CP and Bootstrap providers.

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 #