Add Track and Follow options in gui EntityContextMenu

[bperseghetti]

🎉 New feature

Summary

I would like to thank NXP for their support in enabling this work.

Depends on:

• Enhanced tracking camera and user visualization experience gz-gui#619
• CameraTrack message for advanced tracking and following. gz-msgs#440

This adds a new /gui/track topic using the CameraTrack message to control multiple types of tracking and associated pgain(s), target(s) and offset(s). Furthermore it publishes a tracking camera status CameraTrack message on /gui/currently_tracked

This also adds an 3 unique follow modes and a tracking mode all able to be set from either the /gui/track topic or more ideally from the user gui.

The 3 follow modes are in a submenu under the right click top level menu Follow Options > and are:

• Follow - Traditional follow mode where camera follows and tracks the same target.
  

• Free Look - Enables a user to follow a target while still using an input device (IE mouse) to look around.
  

• Look At - Only enabled after already selecting a primary object to follow, this allows a user to track a unique secondary target while following the primary target.
  

The other right click top level menu item added is Track, where the gui camera can be moved anywhere in the simulator but will always track the selected object.

These all respect using the escape key to stop any form of tracking.

Test it

Use these changes for collection-harmonic.yaml:

repositories:
  gz-gui:
    type: git
    url: https://github.com/rudislabs/gz-gui.git
    version: pr-track-follow
  gz-msgs:
    type: git
    url: https://github.com/rudislabs/gz-msgs.git
    version: pr-track-follow
  gz-sim:
    type: git
    url: https://github.com/rudislabs/gz-sim.git
    version: pr-track-follow

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• 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.

[j-rivero]

@osrf-jenkins run tests

[bperseghetti]

@osrf-jenkins run tests

Dismissed review as all requested changes were made.