bump Apigee core to the new unified Apigee module in fabric

[danistrebel]

What's changed, or what was fixed?

• bump Apigee core to the new unified Apigee module in fabric

• moved the Env-Env Group attachment from the Env Group to the Env.

• Added Env Node Config support

• More explicitly testing for the env attachments

• Utility function to run tf fmt on all modules and samples

• [x] I have run all the tests locally and they all pass.

• [x] I have followed the relevant style guide for my changes.

[danistrebel]

FYI: Marked as draft to wait for the official release in fabric that contains the new Apigee Module.

[g-greatdevaks]

Some supporting fixes have been merged as part of https://github.com/apigee/terraform-modules/pull/93 to enable usage of optional Terraform variable type.