🌱 improve templates ui in tilt

[fabriziopandini]

What this PR does / why we need it:
Small improvements in templates UI in tilt:

• templates show up using provider labels, so things are in order e.g. CAPD, CAPD.clusterclass, CAPD.templates
• add inputs to buttons so it is possible to change substitutions values on the fly

[ykakarap]

Nice improvements.

Some cosmetic improvements:

• Now because the same cluster name is reused, unless changed by the user, the yaml created will keep modifying the same cluster over and over again. It would be nice to rename some of the button and logs to become "applying cluster " instead of "creating cluster " to avoid any confusion.

• Similarly the button "Delete" + template_name + "clusters" wont behave the same way as the cluster names no longer follow a predicable pattern. It would be nice to also add a text-input to the Delete button so that one can delete a target cluster.

[killianmuldoon]

/lgtm

[chrischdi]

Great improvement 👍 Already thought about that too.

/lgtm

[Jont828]

@fabriziopandini This change looks great! In tilt.md where we document that the substitutions in kustomize_substitutions will be used in deploying templates. I noticed an issue where it only works for CLUSTER_NAME, NAMESPACE, KUBERNETES_VERSION, CONTROL_PLANE_MACHINE_COUNT, WORKER_MACHINE_COUNT, and any other substitution wouldn't go through because we don't actually set it as an environment variable anywhere.

For example, if you set CLUSTER_IDENTITY_NAME: cluster-identity and reference it in your template, CLUSTER_IDENTITY_NAME would be undefined and we get an error like this:

Error: value for variables [AZURE_CLUSTER_IDENTITY_SECRET_NAME, AZURE_CLUSTER_IDENTITY_SECRET_NAMESPACE, AZURE_CONTROL_PLANE_MACHINE_TYPE, AZURE_NODE_MACHINE_TYPE, CLUSTER_IDENTITY_NAME] is not set. Please set the value using os environment variables or the clusterctl config file

I opened #6968 to fix it, but do you think you could add this change here?

[fabriziopandini]

@Jont828 @ykakarap PTAL
I have restored random name generation + set os variables + make sure all commands works in different namespaces
I have also open tilt-dev/tilt#5907 to make UX more intuitive, but this should not block current PR

[chrischdi]

/lgtm

[vincepri]

/approve

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[Jont828]

Thanks for making this change!