Consolidate RobotState benchmarks in single file

[marioprats]

Description

This change consolidates robot_state_benchmark.cpp and robot_state_jacobian_benchmark.cpp into a single robot_state_benchmark.cpp file, and adds further benchmarks for RobotState construction, copy, and forward kinematics. This is in preparation for a follow-up change to update memory management in RobotState.
The matrix multiplication / inverse tests have been fully rewritten into a gmock BENCHMARK for consistency.

Output of running:

./build/moveit_core/robot_state/robot_state_benchmark 2>/dev/null
---------------------------------------------------------------------------------
Benchmark                                       Time             CPU   Iterations
---------------------------------------------------------------------------------
MultiplyAffineTimesMatrix/10000000           55.7 ms         55.7 ms           13
MultiplyMatrixTimesMatrix/10000000           57.3 ms         57.3 ms           12
MultiplyIsometryTimesIsometry/10000000       57.5 ms         57.5 ms           12
InverseIsometry3d/10000000                    107 ms          107 ms            7
InverseAffineIsometry/10000000               23.3 ms         23.3 ms           30
InverseAffine/10000000                       52.7 ms         52.7 ms           14
InverseMatrix4d/10000000                      109 ms          109 ms            6
RobotStateConstruct/100                     0.005 ms        0.005 ms       123429
RobotStateConstruct/1000                    0.054 ms        0.054 ms        12827
RobotStateConstruct/10000                   0.553 ms        0.553 ms         1250
RobotStateCopy/100                          0.006 ms        0.006 ms       114604
RobotStateCopy/1000                         0.061 ms        0.061 ms        11284
RobotStateCopy/10000                        0.615 ms        0.615 ms         1141
RobotStateUpdate/10                         0.026 ms        0.026 ms        26048
RobotStateUpdate/100                        0.269 ms        0.269 ms         2615
RobotStateUpdate/1000                        2.66 ms         2.66 ms          262
RobotStateForwardKinematics/10              0.023 ms        0.023 ms        29936
RobotStateForwardKinematics/100             0.234 ms        0.234 ms         2996
RobotStateForwardKinematics/1000             2.34 ms         2.34 ms          304
MoveItJacobian                                258 ns          258 ns      2714295
KdlJacobian                                  1106 ns         1107 ns       630134

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f79a070) 50.83% compared to head (6658e1a) 50.44%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2528      +/-   ##
==========================================
- Coverage   50.83%   50.44%   -0.39%     
==========================================
  Files         391      390       -1     
  Lines       32198    32026     -172     
==========================================
- Hits        16366    16151     -215     
- Misses      15832    15875      +43     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[sjahr]

Thanks for this cleanup! The unification of the files makes sense to me. Could you add documentation for this file to make maintainability easier in the future? I think ~ one brief comment for every function + benchmark and explanation for some parameters is sufficient.

[sjahr]

Thanks!