Refs #13972: Fix GuidPrefix fail case in >>operator [13972]

[jparisu]

Fix GuidPrefix fail case in >>operator

Description

GuidPrefix_t class has a deserialization method >> operator that does not fail in case an incorrect string format is passed.
This is fixed by returning an unknown (invalid) GuidPrefix.

Contributor Checklist

• Commit messages follow the project guidelines.
• The code follows the style guidelines of this project.
• Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added.
• Any new/modified methods have been properly documented using Doxygen.
• Fast DDS test suite has been run locally.
• Changes are ABI compatible.
• Changes are API compatible.
• Documentation builds and tests pass locally.
• New feature has been added to the versions.md file (if applicable).
• New feature has been documented/Current behavior is correctly described in the documentation.

Reviewer Checklist

• Check contributor checklist is correct.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

[jparisu]

There are no tests for GuidPrefix_t, so no tests are added

[EduPonz]

LGTM