[21351] Refactor TopicDataType

[richiware]

Description

Implementation of XCDR introduces new functions in TopicDataType class. But the old one remained. This PR removes them before launching the major version 3, and also performs additional refactorings:

• Change method names to snake_case and have more meaningful names.
• Change arguments from pointer to reference where applicable
• Use std::string instead of char* on name getters and setters

Contributor Checklist

• Commit messages follow the project guidelines.
• Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally
• N/A New feature has been documented/Current behavior is correctly described in the documentation.
• 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.