Alerting: Fix DatasourceUID and RefID missing for DatasourceNoData alerts

[grobinson-grafana]

Which issue(s) does this PR fix?:

This commit fixes a bug where DatasourceUID and RefID annotations are missing for DatasourceNoData alerts in Grafana 9.5. This bug affects datasource plugins that have moved to using the data plane contract.

This bug appears to have been introduced in #62254 which updates the Prometheus plugin to send back no data data frames as documented in the data plane contract.

Fixes #66629

Special notes for your reviewer:

Please check that:

• It works as expected from a user's perspective.
• If this is a pre-GA feature, it is behind a feature toggle.
• The docs are updated, and if this is a notable improvement, it's added to our What's New doc.

[grafanabot]

Hello @grobinson-grafana!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If the pull request modifies CI behaviour, please add the type/ci label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!

[grobinson-grafana]

The lack of unit tests is because this function isn't even tested. I'm going to create the tests for this in another PR and then rebase main onto this when those tests are committed.

[gotjosh]

Tagging @itsmylife, @kylebrandt and @ryantxu (for an FYI) as this was introduced in #62254.

We're happy to review other changes you make around this area as you implement more of the data plane contract on other data sources t to ensure we're not affected. We promise not to slow you down and review promptly 🙏

[yuri-tceretian]

LGTM