[20351] Fix on_sample_lost notification on best-effort readers for framented samples (backport #4187)

[mergify[bot]]

Description

When some fragments are lost on every sample, best-effort readers were not notifying on_sample_lost events.

@Mergifyio backport 2.12.x 2.11.x 2.10.x 2.6.x

Contributor Checklist

• [x] Commit messages follow the project guidelines.

• [x] The code follows the style guidelines of this project.

• [x] 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 Any new/modified methods have been properly documented using Doxygen.

• [x] Changes are ABI compatible.

• [x] Changes are API compatible.

• N/A New feature has been added to the versions.md file (if applicable).

• N/A New feature has been documented/Current behavior is correctly described in the documentation.

• [x] Applicable backports have been included in the description.

Reviewer Checklist

• [x] The PR has a milestone assigned.
• [x] Check contributor checklist is correct.
• [ ] Check CI results: changes do not issue any warning.
• [ ] Check CI results: failing tests are unrelated with the changes.

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This is an automatic backport of pull request #4187 done by [Mergify](https://mergify.com).

[Mario-DL]

@richiprosima please test this

[MiguelCompany]

This one now depends on #4825

[Mario-DL]

Sorry, saw the comment after requesting ci, I will abort and w8 for the other

[Mario-DL]

@richiprosima please test discovery-server