feat(workflows): add user_env_vars field + tests

[kumailkermalli-datatonic]

This PR:

• Modifies google_workflows_workflow to add user_env_vars field which is currently in preview. This allows users to set custom environment variables for Workflows
• Add tests (basic and update) as appropriate

Note that since user_env_vars is in preview (see here), this new field will only be present in the beta provider

Fixes: hashicorp/terraform-provider-google#16341
Fixes: hashicorp/terraform-provider-google#15912

Release Note Template for Downstream PRs (will be copied)

workflows: added field `user_env_vars` to `google_workflows_workflow` (beta)

[modular-magician]

Hello! I am a robot. It looks like you are a: Community Contributor Googler Core Contributor. Tests will require approval to run.

@slevenick, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

You can help make sure that review is quick by doing a self-review and by running impacted tests locally.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 1 file changed, 61 insertions(+))
Terraform Beta: Diff ( 4 files changed, 299 insertions(+))
TF Conversion: Diff ( 1 file changed, 17 insertions(+))
TF OiCS: Diff ( 4 files changed, 148 insertions(+))

[modular-magician]

Tests analytics

Total tests: 3173
Passed tests 2850
Skipped tests: 320
Affected tests: 3

Action taken

Found 3 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

TestAccDefaultUniverseDomainDisk|TestAccWorkflowsWorkflow_workflowBetaExample|TestAccWorkflowsWorkflowBeta_update

Get to know how VCR tests work

[modular-magician]

$\textcolor{green}{\textsf{Tests passed during RECORDING mode:}}$
TestAccDefaultUniverseDomainDisk[Debug log]
TestAccWorkflowsWorkflow_workflowBetaExample[Debug log]
TestAccWorkflowsWorkflowBeta_update[Debug log]

Rerun these tests in REPLAYING mode to catch issues

$\textcolor{green}{\textsf{No issues found for passed tests after REPLAYING rerun.}}$

---

$\textcolor{green}{\textsf{All tests passed!}}$
View the build log or the debug log for each test

[kumailkermalli-datatonic]

Hi @slevenick - all tests have passed. Would it be possible to get a review on this?