Provide an option to omit username for redis passwordless

[saragluna]

Description

Now the redis passwordless requires users to provide a username, this is not convenient for system assigned identity. This PR provides an option to retrieve the username from the JWT token, claim "oid".

All SDK Contribution checklist:

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

General Guidelines and Best Practices

• [x] Title of the pull request is clear and informative.
• [x] 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.

[saragluna]

To test this change, please follow these steps to build the dependencies locally:

• Check out the source branch, git clone git@github.com:saragluna/azure-sdk-for-java.git, or add the git remote git remote add xiada git@github.com:saragluna/azure-sdk-for-java.git.
• Fetch and switch to the branch, git fetch origin or git fetch xiada. git switch xiada/redis-omit-username.
• Build and install the spring projects mvn clean install -Dcheckstyle.skip=true -Dcodesnippet.skip -Denforcer.skip -Djacoco.skip=true -Dmaven.javadoc.skip=true -Drevapi.skip=true -DskipTests -Dspotbugs.skip=true -T 1 -ntp -Pdev -f sdk/spring/pom.xml.
• Change the spring cloud azure version to 5.14.0-beta.1

After using the latest version, spring.data.redis.username can be omitted.