[20729] Allow processing of AckNack submessages with count == 0 (backport #4639)

[mergify]

Description

As spotted by omg-dds/dds-rtps#35, Fast DDS ignores AckNack messages where the count field is 0.

This PR adds a unit test for ReaderProxy::check_and_set_acknack_count, and fixes the issue by changing the check on acknack_count from last received to next expected.

@Mergifyio backport 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.

• Changes are ABI compatible.

• 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.

---

This is an automatic backport of pull request #4639 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 66fc7c5 has failed:

On branch mergify/bp/2.6.x/pr-4639
Your branch is up to date with 'origin/2.6.x'.

You are currently cherry-picking commit 66fc7c533.
  (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:   include/fastdds/rtps/writer/ReaderProxy.h
	modified:   src/cpp/rtps/writer/ReaderProxy.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   test/unittest/rtps/writer/ReaderProxyTests.cpp

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

[Mario-DL]

@richiprosima please test this

[Mario-DL]

LGTM. Failed tests unrelated to this PR.