Set mandatory fields on RAD Lab UI via UIMeta flag

[guptamukul-google]

Is your feature request related to a problem? Please describe.
Currently the Fields are marked mandatory based on 2 different parameters:

1. There is no default value in variables.tf file
2. Some preset mandatory fields on the templates.

Describe the solution you'd like
Create a new UIMeta flag which will determine if the input variable will be mandatory or not. This is also a good time to think about the depends_on flag where a variable needs to be mandatory depending on another variable set.

[github-actions]

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