Add more tests to azure-core-version-tests

[alzimmermsft]

Description

Fixes #35399

Adds more test cases to azure-core-version-tests for further version support validation.

This PR also fixes a behavioral change in parsing of XML String arrays where empty and self-closing tags were treated as empty string and then changed to null. A deserialization modifier was added to coerce null back to empty string.

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.

[lmolkova]

LGTM!