feat: support EXP_MACHINE_POOL flag

This PR makes sure we set the machine pool flag for our bootstrap
provider. This is needed to make sure we work out of the box with ASGs
in AWS when users install our providers w/ clusterctl.

Signed-off-by: Spencer Smith <[email protected]>

Author: rsmitty

config/manager/manager.yaml

@@ -20,6 +20,7 @@ spec:
             - /manager
           args:
             - --enable-leader-election
+            - "--feature-gates=MachinePool=${EXP_MACHINE_POOL:=false}"
           image: controller:latest
           imagePullPolicy: Always
           name: manager