Do not fail packer datasources for iteration with revoke_at set to the future

[sylviamoss]

🛠️ Description

The hcp_packer_x datasources were checking if an iteration had a revoke_at to tell if it's revoked or not. This was wrong because a revoke_at set to the future means that revocation is scheduled and the iteration is currently valid.
This PR fixes this behaviour and only fails for revoked_at <= now

🚢 Release Note

Release note for CHANGELOG:

* datasource/hcp_packer_image: Fix check for revoked iterations to consider scheduled revocation valid [GH-262]
* datasource/hcp_packer_iteration: Add check for revoked iterations to consider scheduled revocation valid [GH-262]
* datasource/hcp_packer_image_iteration: Add check for revoked iterations to consider scheduled revocation valid [GH-262]

🏗️ Acceptance tests

• Are there any feature flags that are required to use this functionality?
• Have you added an acceptance test for the functionality being added?
• Have you run the acceptance tests on this branch?

Output from acceptance testing:

TF_ACC=1 go test ./internal/... -v -run=TestAcc_dataSourcePacker -timeout 120m
?       github.com/hashicorp/terraform-provider-hcp/internal/clients    [no test files]
testing: warning: no tests to run
PASS
ok      github.com/hashicorp/terraform-provider-hcp/internal/consul     (cached) [no tests to run]
testing: warning: no tests to run
PASS
ok      github.com/hashicorp/terraform-provider-hcp/internal/input      (cached) [no tests to run]
=== RUN   TestAcc_dataSourcePacker
--- PASS: TestAcc_dataSourcePacker (29.76s)
=== RUN   TestAcc_dataSourcePacker_revokedIteration
--- PASS: TestAcc_dataSourcePacker_revokedIteration (13.60s)
=== RUN   TestAcc_dataSourcePacker_iterationScheduledToBeRevoked
--- PASS: TestAcc_dataSourcePacker_iterationScheduledToBeRevoked (26.23s)
=== RUN   TestAcc_dataSourcePackerImage
--- PASS: TestAcc_dataSourcePackerImage (27.55s)
=== RUN   TestAcc_dataSourcePackerIteration
--- PASS: TestAcc_dataSourcePackerIteration (27.64s)
=== RUN   TestAcc_dataSourcePackerIteration_revokedIteration
--- PASS: TestAcc_dataSourcePackerIteration_revokedIteration (13.19s)
=== RUN   TestAcc_dataSourcePackerIteration_iterationScheduledToBeRevoked
--- PASS: TestAcc_dataSourcePackerIteration_iterationScheduledToBeRevoked (26.87s)
PASS
ok      github.com/hashicorp/terraform-provider-hcp/internal/provider   165.150s

[azr]

Nice one! LGTM!

[bcmdarroch]

Nice work!