ARM template IaC support

[wbreza]

Pluggable support for legacy customer to continue to use their ARM templates vs forcing them to upgrade to bicep.

[jongio]

Although untested, this should just work today by overriding env vars to point to the file.

I would like to implement a discovery API that looks at what is in the provisioning folder and auto figuring out what they want to do. For example, if I find a bicep file, then probably the whole thing is bicep. If I find ARM files, then arm, etc.