chore: Supports running cloud gov tests in CI

Description

Supports running cloud gov tests in CI.

Follow-up PR with a gov migration and acceptance test: #2291

Uses a fully configured provider when using cloud-gov, why?

Enables running gov tests in the same process as cloud-dev/cloud-qa tests
Keeps the CI simple with a single acceptance-tests job and we can run the tests often

Alternatives considered:

Modify env-vars for each cloud-gov test run (similar to t.Setenv("MONGODB_ATLAS_LAST_VERSION", "1.2.3") but with MONGODB_ATLAS_PRIVATE/PUBLIC_KEY/BASE_URL++
- Does not allow running tests in parallel since env-vars would impact the "normal" acceptance tests
Run a separate process/workflow
- Would require different CI workflows, but config would be a bit shorter as the provider would read env-vars directly

Link to any related issue(s): CLOUDP-250271

[ ] Bug fix (non-breaking change which fixes an issue). Please, add the "bug" label to the PR.
[ ] New feature (non-breaking change which adds functionality). Please, add the "enhancement" label to the PR. A migration guide must be created or updated if the new feature will go in a major version.
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected). Please, add the "breaking change" label to the PR. A migration guide must be created or updated.
[ ] This change requires a documentation update
[ ] Documentation fix/enhancement

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