feat(ci): per provider integration tests

[geekbrother]

Description

The context of the issue (#464):

At the moment we are running providers integration tests on all changes. Sometimes some of the providers are unavailable (rate-limited etc.) that results in a blocking of the CI/CD process.
We should run the provider tests only when the provider implementation is changed and run the test only for that provider that was changed.

This PR introduces the following changes:

• Making all provider tests optional by making them #[ignore]
• Unifying providers test names to the {provider_name}_provider pattern
• Adding the sub-providers.yml workflow that:
  • Determining what provider was changed
  • Run the specific provider test (or multiple providers that were changed)
  • This workflow can be called manually from actions by providing the list of providers to test
  • This workflow will be called as a dependency step from sub-validate.yml when merged and after testing it manually (to not block the CI until tested and possible fixes are merged) by the following feat(ci): run provider specific tests from sub-validate #466 PR.
• Adding README file with the descriptions on how providers testing work

Resolves #464

How Has This Been Tested?

Tested only partly because of the GitHub CI nature.
The sub-providers.yml workflow was tested isolated and reduced in the forked repo by pushing different commits on it:

• No provider changed
• One provider changed
• Few providers changed

Due Diligence

• Breaking change
• Requires a documentation update
• Requires a e2e/integration test update

[geekbrother]

I think we don't need to fail all providers in case of one for cases like: we are manually validating a list of providers and want to know if there is a global issue or just one provider fails.

[geekbrother]

Removing whitespace at the end.

[geekbrother]

Making JSON array from a space separated list.

[chris13524]

Have you considered jq?

[geekbrother]

I think it's not installed by default, so it's not worth to install it for one line.

[geekbrother]

I leave this step for debugging purposes.