Add OPA support for policy sets

[mrinalirao]

Description

Add OPA support to the tfe-provider for policy sets. OPA is still in beta phase.
The existing tfe_policy_set provider will allow for creation of both sentinel as well as OPA policies in the provider.

This is the second of the 3 PRs for adding OPA support:
Previous PRs: #690

Upcoming PRs

• Update documentation

Testing plan

Acceptance tests added

External links

Include any links here that might be helpful for people reviewing your PR. If there are none, feel free to delete this section.

• go-tfe documentation
• API documentation
• JIRA
• Related PR

Output from acceptance tests

$ TESTARGS="-run TestAccTFEPolicySetOPA_basic" envchain staging make testacc

TF_ACC=1 TF_LOG_SDK_PROTO=OFF go test $(go list ./... |grep -v 'vendor') -v -run TestAccTFEPolicySetOPA_basic -timeout 15m
?       github.com/hashicorp/terraform-provider-tfe     [no test files]
=== RUN   TestAccTFEPolicySetOPA_basic
    testing.go:181: Skipping test related to a Terraform Cloud/Enterprise beta feature. Set ENABLE_BETA=1 to run.
--- SKIP: TestAccTFEPolicySetOPA_basic (0.00s)
PASS
ok      github.com/hashicorp/terraform-provider-tfe/tfe 0.604s
?       github.com/hashicorp/terraform-provider-tfe/version     [no test files]

$ TESTARGS="-run TestAccTFEPolicySetDataSourceOPA_basic" envchain staging make testacc

TF_ACC=1 TF_LOG_SDK_PROTO=OFF go test $(go list ./... |grep -v 'vendor') -v -run TestAccTFEPolicySetDataSourceOPA_basic -timeout 15m
?       github.com/hashicorp/terraform-provider-tfe     [no test files]
=== RUN   TestAccTFEPolicySetDataSourceOPA_basic
    testing.go:181: Skipping test related to a Terraform Cloud/Enterprise beta feature. Set ENABLE_BETA=1 to run.
--- SKIP: TestAccTFEPolicySetDataSourceOPA_basic (0.00s)
PASS
ok      github.com/hashicorp/terraform-provider-tfe/tfe 0.272s
?       github.com/hashicorp/terraform-provider-tfe/version     [no test files]

[brandonc]

Found just the one issue with overridable.

[mrinalirao]

Added an acceptance test for setting overridable:

=== RUN   TestAccTFEPolicySet_updateOverridable
2022/11/29 09:32:08 [DEBUG] Configuring client for host "app.staging.terraform.io"
2022/11/29 09:32:08 [ERROR] Error reading CLI config or credentials file /Users/mrinalirao/.terraformrc: open /Users/mrinalirao/.terraformrc: no such file or directory
2022/11/29 09:32:08 [DEBUG] Service discovery for app.staging.terraform.io at https://app.staging.terraform.io/.well-known/terraform.json
--- PASS: TestAccTFEPolicySet_updateOverridable (24.11s)
PASS