Extend external patch implementation in RuntimeSDK e2e test

[sbueringer]

Our RuntimeSDK e2e test tests external patching by calling a test extension.

Initially we only moved one patch from the ClusterClass to the test extension

Goal of this issue is to move all inline patches of the RuntimeSDk ClusterClass to the test extension handler, to increase test coverage and get some experience on how to implement external patches.

Note:

• Let's also implement some validations in the ValidateTopology extension handler

Links:

• test extension: external patching handler: https://github.com/kubernetes-sigs/cluster-api/blob/main/test/extension/handlers/topologymutation/handler.go
• ClusterClass used in the RuntimeSDK e2e test: https://github.com/kubernetes-sigs/cluster-api/blob/main/test/e2e/data/infrastructure-docker/v1beta1/clusterclass-quick-start-runtimesdk.yaml#L79-L199

[killianmuldoon]

/assign

I'll get working on this

[fabriziopandini]

/triage accepted