[21313] Allow all @default annotation values for unions

[EduPonz]

Description

This PR enables the use of any @default annotation value for unions.
Required by:

• [21313] Type propagation policy Fast-DDS#5081

Depends on:

*eProsima/dds-types-test#34

Contributor Checklist

• Commit messages follow the project guidelines.
• N/A: Any new/modified methods have been properly documented.
• N/A: Changes are backport compatible: they do NOT break ABI nor change library core behavior.
• N/A: Changes are API compatible.
• N/A: Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.