✨ RuntimeSDK: Add extension config controller skeleton

[killianmuldoon]

This PR adds a skeleton controller to handle the ExtensionConfig object added in #6383. This controller will eventually be used to handle status updates to the ExtensionConfig CRD.

Note: This PR includes #6383 and should not be merged until that PR is merged. This PR will require a rebase before merging.

Part of: #6330

[killianmuldoon]

/retest

[sbueringer]

@ykakarap Based on comments on the other PR I assume you have access to Kilian's repo. Could you maybe rebase this PR?

[sbueringer]

Looks good.
Pending rebase (and dropping the first 5 commits) + fixing the nits, lgtm from my side

[ykakarap]

@sbueringer I rebased and addressed all the comments. I dont have permissions to resolve conversations, can you please mark them as resolved if you are happy with them?

[sbueringer]

/retitle RuntimeSDK: Add extension config controller skeleton

/lgtm

/assign @fabriziopandini
When you've got some time. I think this is ready to go.

@killianmuldoon @ykakarap Thank you very much!

[chrischdi]

/lgtm

[fabriziopandini]

/lgtm
/approve

[k8s-ci-robot]

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