✨ Allow overriding image name in clusterctl config

[alexander-demicev]

What this PR does / why we need it:
This PR adds a name override option for the clusterctl config:

images:
  cluster-api:
    repository: myorg.io/local-repo
    name: mirrored-cluster-api-controller
    tag: v1.10.6

We have use-case where using clusterctl config is the best option to override CAPI image name for some air-gapped scenarios where image is retagged with a slightly different name.

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 #

/area clusterctl

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[alexander-demicev]

/area clusterctl

[salasberryfin]

Thanks @alexander-demicev.

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: f0443ca25466e6ce217493cb8df62c259ca89dff