Sign clusterctl binaries with cosign

What would you like to be added (User Story)?

We are already signing our images with cosign, and this issue tracks the signing of clusterctl binary with cosign. This will be followed by documenting verifications steps which is being tracked in #9292

Detailed Description

Sign clusterctl binary with cosign and all *.sig and *.cert file for verification.

Ref: https://kubernetes.io/docs/tasks/administer-cluster/verify-signed-artifacts/#verifying-binary-signatures

cc @nawazkh @furkatgofurov7 // for 1.6 release

Anything else you would like to add?

No response

Label(s) to be applied

/kind feature One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.