Made dataflow job updates fail fast if they're cancelled

[modular-magician]

Resolved hashicorp/terraform-provider-google#9227.

Dataflow flex template jobs that are CANCELLING or DRAINING will never be able to be RUNNING. If we're expecting RUNNING but seeing CANCELLING or DRAINING, we can fail fast and let the user know (instead of making them wait for a few minutes.)

An alternative implementation would be to "update" the job by actually creating a new job (i.e. not using the update mechanism provided by dataflow flex templates.) However, that seems potentially confusing for end users. That would need some discussion as a potential enhancement, rather than a bug.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

dataflow: made `google_dataflow_flex_template_job` updates fail fast if the job is in the process of cancelling or draining (beta)

Derived from GoogleCloudPlatform/magic-modules#4845