Clean up namespaces - part 2 (backport #642)

[mergify]

Splitting the work created from @mjcarroll in #502. This is tweaking the header files under gz/transport.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

---

This is an automatic backport of pull request #642 done by Mergify.

[mergify]

Cherry-pick of bd39167 has failed:

On branch mergify/bp/gz-transport14/pr-642
Your branch is up to date with 'origin/gz-transport14'.

You are currently cherry-picking commit bd39167.
  (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/gz/transport/HandlerStorage.hh
	modified:   include/gz/transport/Helpers.hh
	modified:   include/gz/transport/MessageInfo.hh
	modified:   include/gz/transport/NetUtils.hh
	modified:   include/gz/transport/NodeOptions.hh
	modified:   include/gz/transport/NodeShared.hh
	modified:   include/gz/transport/Publisher.hh
	modified:   include/gz/transport/RepHandler.hh
	modified:   include/gz/transport/ReqHandler.hh
	modified:   include/gz/transport/SubscribeOptions.hh
	modified:   include/gz/transport/SubscriptionHandler.hh
	modified:   include/gz/transport/TopicStatistics.hh
	modified:   include/gz/transport/TopicStorage.hh
	modified:   include/gz/transport/TopicUtils.hh
	modified:   include/gz/transport/TransportTypes.hh
	modified:   include/gz/transport/Uuid.hh

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   include/gz/transport/Node.hh

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

[codecov]

Codecov Report

Attention: Patch coverage is 88.62144% with 52 lines in your changes missing coverage. Please review.

Please upload report for BASE (gz-transport14@c910b6d). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
include/gz/transport/ReqHandler.hh	81.48%	20 Missing ⚠️
include/gz/transport/RepHandler.hh	67.27%	18 Missing ⚠️
include/gz/transport/SubscriptionHandler.hh	77.41%	14 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                @@
##             gz-transport14     #643   +/-   ##
=================================================
  Coverage                  ?   86.91%           
=================================================
  Files                     ?       59           
  Lines                     ?     5948           
  Branches                  ?        0           
=================================================
  Hits                      ?     5170           
  Misses                    ?      778           
  Partials                  ?        0           

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