feat: Apply MetalLB configuration to remote cluster

[dlipovetsky]

What problem does this PR solve?:

• Generates MetalLB configuration from ServiceLoadBalancer Configuration API (added in feat: Define ServiceLoadBalancer Configuration API #763)
• Waits for MetalLB helm chart to be successfully deployed (using waiter added in feat: Add waiter for object #762)
• Applies MetalLB configuration to remote cluster, also using a wait.

To apply MetalLB configuration, the MetalLB CRD webhooks must be ready. This is not guaranteed to happen once the MetalLB helm chart is successfully deployed.

Because the MetalLB configuration is applied in a non-blocking lifecycle hook, the topology controller retries the hook immediately after it returns; we cannot ask for a delay. Because the topology controller backs off its requests exponentially, this often results in the hook requests being delayed for 3+ minutes before succeeding.

To mitigate this exponentiall backoff, the hook retries internally for to up to 20 seconds, within the 30 seconds recommended by the Cluster API.

Related log excerpt

    I0628 19:39:31.051929       1 handler.go:132] "Deploying ServiceLoadBalancer provider MetalLB" cluster="default/dlipovetsky"
    I0628 19:39:31.051954       1 handler.go:82] "Applying MetalLB installation" cluster="default/dlipovetsky"
    I0628 19:39:31.100706       1 cm.go:82] "Fetching HelmChart info for \"metallb\" from configmap default/default-helm-addons-config" cluster="default/dlipovetsky"
    E0628 19:39:41.031497       1 handler.go:140] "failed to deploy ServiceLoadBalancer provider MetalLB" err="context canceled: last apply error: failed to apply MetalLB configuration IPAddressPool metallb-system/metallb: server-side apply failed: Patch \"https://172.18.0.2:6443/apis/metallb.io/v1beta1/namespaces/metallb-system/ipaddresspools/metallb?fieldManager=cluster-api-runtime-extensions-nutanix&fieldValidation=Strict&timeout=10s\": context canceled" cluster="default/dlipovetsky"
    ...
    E0628 19:43:49.496027       1 handler.go:140] "failed to deploy ServiceLoadBalancer provider MetalLB" err="context canceled: last apply error: failed to apply MetalLB configuration IPAddressPool metallb-system/metallb: server-side apply failed: Internal error occurred: failed calling webhook \"ipaddresspoolvalidationwebhook.metallb.io\": failed to call webhook: Post \"https://metallb-webhook-service.metallb-system.svc:443/validate-metallb-io-v1beta1-ipaddresspool?timeout=10s\": dial tcp 10.130.84.48:443: connect: connection refused" cluster="default/dlipovetsky"
    I0628 19:43:51.785907       1 handler.go:132] "Deploying ServiceLoadBalancer provider MetalLB" cluster="default/dlipovetsky"
    I0628 19:43:51.785923       1 handler.go:82] "Applying MetalLB installation" cluster="default/dlipovetsky"
    I0628 19:43:51.790521       1 cm.go:82] "Fetching HelmChart info for \"metallb\" from configmap default/default-helm-addons-config" cluster="default/dlipovetsky"

Which issue(s) this PR fixes:
Fixes #

How Has This Been Tested?:

Special notes for your reviewer:

[jimmidyson]

Closing as merged in #783.