Support GovCloud us-gov-west-1 (PDT) with v1.4.0 release

[hwandersman]

What this PR does / why we need it:
IoT TwinMaker is launching to the GovCloud us-gov-west-1 region, so we need to add this region as an option in the datasource region dropdown. The AWS SDK already supports this region so the backend/frontend code will not need to be updated any more.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:
We do not want to merge this change and release the version until Wednesday 03/22. We will discuss exact timing soon.

[github-actions]

Backend code coverage report for PR #178
No changes

[github-actions]

Frontend code coverage report for PR #178

Plugin	Main	PR	Difference
src	44.59%	44.59%	0%

[github-actions]

Levitate is-compatible report:

🔍 Resolving @grafana/data@latest...
🔍 Resolving @grafana/ui@latest...
🔍 Resolving @grafana/runtime@latest...
🔍 Resolving @grafana/e2e-selectors@latest...

🔬 Checking compatibility between ./src/module.ts and @grafana/data@9.4.3...
✔ Found @grafana/data version 8.4.11 locally

🔬 Checking compatibility between ./src/module.ts and @grafana/ui@9.4.3...
✔ Found @grafana/ui version 8.4.11 locally

🔬 Checking compatibility between ./src/module.ts and @grafana/runtime@9.4.3...
✔ Found @grafana/runtime version 8.4.11 locally

🔬 Checking compatibility between ./src/module.ts and @grafana/e2e-selectors@9.4.3...
✔ Found @grafana/e2e-selectors version 8.4.11 locally

✔️ ./src/module.ts appears to be compatible with @grafana/data,@grafana/ui,@grafana/runtime,@grafana/e2e-selectors