fix(autoware_pointcloud_preprocessor): fix potential double unlock in concatenate node

[vividf]

Description

This PR resolves a potential double unlock issue in the concatenate node. Previously, under certain conditions, the mutex could be unlocked twice, leading to undefined behavior and potential segmentation faults.

Related links

Note: This PR needs to rebase after #10074 is merged.

Parent Issue:

• Link

How was this PR tested?

• Tested with unit test.
• Tested with sample rosbag

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

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[codecov]

Codecov Report

Attention: Patch coverage is 18.18182% with 18 lines in your changes missing coverage. Please review.

Project coverage is 26.76%. Comparing base (c6665a7) to head (a98988c).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...oncatenate_data/concatenate_and_time_sync_node.cpp	10.00%	16 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10082      +/-   ##
==========================================
- Coverage   26.77%   26.76%   -0.02%     
==========================================
  Files        1397     1397              
  Lines      107977   107994      +17     
  Branches    41580    41577       -3     
==========================================
- Hits        28908    28901       -7     
- Misses      76194    76223      +29     
+ Partials     2875     2870       -5     

Flag	Coverage Δ		*Carryforward flag
differential	21.58% <18.18%> (?)
total	26.76% <ø> (-0.01%)	⬇️	Carriedforward from c6665a7

*This pull request uses carry forward flags. Click here to find out more.

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[knzo25]

@vividf
It seems there are several conflicts

[mojomex]

As remarked by @knzo25 offline some days ago, and as per the discussion @drwnz @vividf @manato and I just had,. it might be better to remove all locking completely as the callbacks within one node will always be in a mutually exclusive callback group by default, even when using a multithreaded executor.
This makes concat effectively single-threaded and thus no locking is needed. Performance hasn't be a problem even with our more data-heavy architectures.

[knzo25]

@mojomex
My comments though, require checking how threading, callback groups and timers work in ros.
In my experience, some timers (there are several, and some work at a lower level) had weird behaviors (different clocks were used ages ago, during some transitions, probably from ros1)

[mojomex]

LGTM!
There's two small aesthetic suggestions I left but the algorithm itself loogs good and works fine 👍