Parallel creation of multiple loadbalancers

[mdbooth]

/kind feature

Describe the solution you'd like
LoadBalancers take many minutes to become available after creation. We currently wait synchronously for a loadbalancer to become available immediately after creation:

cluster-api-provider-aws/pkg/cloud/services/elb/loadbalancer.go

Lines 128 to 133 in 63b8bcf

	waitStart := time.Now()
	if err := s.ELBV2Client.WaitUntilLoadBalancerAvailableWithContext(context.TODO(), wReq); err != nil {
	s.scope.Error(err, "failed to wait for LB to become available", "time", time.Since(waitStart))
	return err
	}
	s.scope.Debug("LB reports active state", "api-server-lb-name", lb.Name, "time", time.Since(waitStart))

This is inefficient when creating more than one ControlPlaneLoadBalancer, for example when creating both the internal and external LBs of an OpenShift cluster. Ideally we would create all loadbalancers first, then wait for them to become ready.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:

• Cluster-api-provider-aws version: v2.8.1-129-g63b8bcf1b (main)

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