Add support for string_255 type and fix discovery status memory leaks (backport #215)

[mergify]

Description

This PR add support for using string_255 type in python applicatioons.

It also fixes the following warnings get when participant listener functions are called:

swig/python detected a memory leak of type 'eprosima::fastdds::rtps::ParticipantDiscoveryStatus *', no destructor found.
swig/python detected a memory leak of type 'eprosima::fastdds::rtps::WriterDiscoveryStatus *', no destructor found.
swig/python detected a memory leak of type 'eprosima::fastdds::rtps::ReaderDiscoveryStatus *', no destructor found.

@Mergifyio backport 2.1.x 2.0.x

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
• Changes are API compatible.
• 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.

---

This is an automatic backport of pull request #215 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 23156aa has failed:

On branch mergify/bp/2.1.x/pr-215
Your branch is up to date with 'origin/2.1.x'.

You are currently cherry-picking commit 23156aa.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   fastdds_python/src/swig/fastdds.i

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   fastdds_python/src/swig/fastcdr/cdr/fixed_size_string.i

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally