Remove 'using namespace' from header files.

[corycrean]

• Remove 'using namespace pilz_industrial_motion_planner' from header files.
• Remove 'using namespace std::chrono_literals' from header files.

Description

This PR addresses #853.

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

Merging #994 (eb5f484) into main (d01ef48) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #994      +/-   ##
==========================================
+ Coverage   57.73%   57.75%   +0.02%     
==========================================
  Files         310      310              
  Lines       26129    26129              
==========================================
+ Hits        15084    15087       +3     
+ Misses      11045    11042       -3     

Impacted Files	Coverage Δ
...z_industrial_motion_planner/trajectory_generator.h	100.00% <ø> (ø)
...ustrial_motion_planner/trajectory_generator_circ.h	100.00% <ø> (ø)
...dustrial_motion_planner/trajectory_generator_lin.h	100.00% <ø> (ø)
...dustrial_motion_planner/trajectory_generator_ptp.h	100.00% <ø> (ø)
...ial_motion_planner/src/joint_limits_aggregator.cpp	95.92% <100.00%> (ø)
...rial_motion_planner/src/joint_limits_container.cpp	100.00% <100.00%> (ø)
...rial_motion_planner/src/joint_limits_validator.cpp	100.00% <100.00%> (ø)
...al_motion_planner/src/trajectory_generator_ptp.cpp	99.02% <100.00%> (ø)
...dl_kinematics_plugin/src/kdl_kinematics_plugin.cpp	74.82% <0.00%> (-1.11%)	⬇️
...ma_kinematics_plugin/src/lma_kinematics_plugin.cpp	76.78% <0.00%> (+3.88%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d01ef48...eb5f484. Read the comment docs.