Foundation Acceptance tests and minor fixes

[bhatipradeep]

Overview :

1. Add acceptance tests for Foundation resource and datasources.
2. Added "test_foundation_config.json" for constants required for foundation and foundation central acceptance tests.
3. Update existing acceptance tests for foundation releated changes
4. Add acceptance test for nutanix_assert_helper and minor fixes in same.
5. Made image_now & cluster_init_now as default to true for image_nodes resource. Updated doc for same.
6. Added field "cluster_urls" to output cluster_url for clusters created in session. For Add important information to the print/output of foundation related resources. #426
7. Update github workflows to become capable of running karbon, pc, foundation, foundation_central tests independently.
8. Change naming of karbon tests from TestAccNutanixKarbon to TestAccKarbon for seperate tests running.

[bhati-pradeep]

/ok-to-test karbon

Acceptance test run status: cancelled

[bhati-pradeep]

/ok-to-test karbon foundation pc

Acceptance test run status: cancelled