[Key Vault] Skip tests when vault SKU is incompatible

[mccoyp]

Description

I recently got our weekly sovereign cloud tests running again, and test runs show that some tests -- namely, those that deal with key release -- require a premium vault SKU in order to work. Standard SKUs are used in China cloud tests, so we need to skip these when necessary.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[azure-sdk]

API change check

API changes are not detected in this pull request.

[mccoyp]

/check-enforcer evaluate

[mccoyp]

/check-enforcer override