Set camera clipping plane distance

[jennuine]

🎉 New feature

Related to gazebosim/gz-gui#308
Closes #1154

Summary

Set the user camera's near/far clipping plane distance through the View Angle plugin.

Test it

1. ign gazebo minimal_shapes.sdf
2. Expand View Angle plugin
3. Enter near/far values in spin boxes

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• 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

[codecov]

Codecov Report

Merging #1162 (8df76f5) into ign-gazebo6 (35ec2a7) will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           ign-gazebo6    #1162   +/-   ##
============================================
  Coverage        63.72%   63.72%           
============================================
  Files              256      256           
  Lines            20116    20116           
============================================
  Hits             12819    12819           
  Misses            7297     7297           

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[chapulina]

Nice!