[20021] TCP support for Discovery server CLI and env. var. (backport #4097)

[mergify]

This is an automatic backport of pull request #4097 done by Mergify.
Cherry-pick of 2653efb has failed:

On branch mergify/bp/2.6.x/pr-4097
Your branch is up to date with 'origin/2.6.x'.

You are currently cherry-picking commit 2653efb95.
  (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/common/Locator.h
	modified:   test/unittest/utils/LocatorTests.cpp

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   examples/C++/DDS/BasicConfigurationExample/BasicConfigurationPublisher.cpp
	both modified:   examples/C++/DDS/BasicConfigurationExample/BasicConfigurationSubscriber.cpp
	deleted by us:   examples/cpp/dds/DiscoveryServerExample/DiscoveryServerServer.cpp
	deleted by us:   examples/cpp/dds/DiscoveryServerExample/DiscoveryServer_main.cpp
	deleted by us:   examples/cpp/dds/DiscoveryServerExample/README.md
	deleted by us:   examples/cpp/dds/DiscoveryServerExample/arg_configuration.h
	deleted by us:   examples/cpp/dds/DiscoveryServerExample/common.h
	both modified:   include/fastdds/rtps/attributes/ServerAttributes.h
	both modified:   src/cpp/rtps/RTPSDomain.cpp
	both modified:   src/cpp/rtps/builtin/discovery/participant/PDPClient.cpp
	both modified:   test/blackbox/common/BlackboxTestsDiscovery.cpp
	both modified:   tools/fds/server.cpp
	both modified:   tools/fds/server.h
	both modified:   versions.md

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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[cferreiragonz]

@richiprosima please test mac please test linux please test discovery_server please check style

[MiguelCompany]

LGTM with green CI

[cferreiragonz]

@richiprosima please test this

[MiguelCompany]

@richiprosima Please test mac