[16608] Fix total_unread_ consistent with reader's history upon get_first_untaken_info() (backport #3203)

[mergify]

This is an automatic backport of pull request #3203 done by Mergify.
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Changes to be committed:
	modified:   src/cpp/fastdds/subscriber/history/DataReaderHistory.cpp
	modified:   test/blackbox/api/dds-pim/PubSubWriter.hpp
	modified:   test/blackbox/common/DDSBlackboxTestsBasic.cpp
	modified:   test/blackbox/common/DDSBlackboxTestsDataReader.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   test/blackbox/api/dds-pim/PubSubReader.hpp

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

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[MiguelCompany]

@richiprosima Please test this