Global values.yaml limit test creation source to only GIT for all test types.

[plamen-kutinchev]

Is your feature request related to a problem? Please describe.
We want to always limit test creation source to only GIT, disable File and String sources for all test types.

Describe the solution you'd like
Can this be done, switched what test sources to be available for all test types via k8s env variable inside the helm chart so we can override them via values.yaml file.

Additional context
We would like to limit the usage for all test type sources to use GIT repository. This will make the automation we create around storing test/test suites and actual tests that Run from PR to be separated and can be easily overridden without interchanging.

[vsukhin]

for @TheBrunoLopes and @jmorante-ks to check. Sounds like a Pro feature to me