Provide a way to use a specific version of CAPZ

[jsturtevant]

We init the version here which takes the latest release

azure-capi-cli-extension/src/capi/azext_capi/custom.py

Line 115 in 045a9ea

command = ["clusterctl", "init", "--infrastructure", "azure"]

Would be nice to use provide a version if specified https://cluster-api.sigs.k8s.io/clusterctl/commands/init.html#provider-version

We may also want to specific the versions of CNI from the repo as well:

azure-capi-cli-extension/src/capi/azext_capi/custom.py

Line 560 in 045a9ea

calico_manifest = "https://raw.githubusercontent.com/kubernetes-sigs/cluster-api-provider-azure/master/templates/addons/calico.yaml" # pylint: disable=line-too-long

possible solutions

Maybe the capz version doesn't need to be managed via an additional flag but instead via the clusterctl configuration file: https://cluster-api.sigs.k8s.io/clusterctl/configuration.html?