[20815] Only apply content filter to ALIVE changes

[EduPonz]

Description

This PR fixes a bug that caused the content filter to also be applied to unregister and disposed samples. Since in those messages the only fields populated (if any) are the ones annotated with @key, the unregister and dispose samples did not pass the filter (in general) and thus were being discarded. This caused several issues:

1. When writing to more than 10 instances with default Qos (keep last 1, max_instances 10), only the first 10 samples were been received.
2. In best effort, when setting the history depth and max instances appropriately, all samples were received, but calls to unregister or dispose followed by a write were triggering sample_lost events, as the received sequence numbers were not consecutive (because of the filtering out of the unregister/dispose).

This PR fixes these issues by only querying for sample relevance when the CacheChange kind is ALIVE.

@EduPonz backport 2.14.x 2.13.x 2.10.x 2.6.x

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; the added tests pass locally
• Any new/modified methods have been properly documented using Doxygen.
• N/A: Any new configuration API has an equivalent XML API (with the corresponding XSD extension)
• Changes are backport compatible: they do NOT break ABI nor change library core behavior.
• 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.
• 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.

[Mario-DL]

This PR brings an interesting bugfix. Leaving a couple of suggestions

[Mario-DL]

LGTM with green CI

[EduPonz]

Backport to 2.14.x:

• [20815] Only apply content filter to ALIVE changes #4876

The rest of the backport will be ordered from there.