Sort out MinimalScene's mouse events

[chapulina]

🦟 Bug fix

Fixes #293

Summary

I started working on the issues pointed out on #293 and ran into various other issues and inconsistencies about the way we're handling mouse events. Currently there are scrolls and drags being sent as left clicks, both mouse presses and releases broadcasted as clicks... I'm still sorting it out, hopefully will be done in time for the release.

Summary of changes:

• Add 3 new events: drag, scroll and press
• Press with any button is used to pick the orbit target
• Drag information was previously being acquired from a combination of the previous event and a left click. Now it's passed through the drag event.
• I think scroll info was also coming from other events, but now it's its own event
• The HandleMouseViewControl was a confusing function that re-sent the left clicks, so I removed it

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[ahcorde]

This PR fixes:

• Scroll zoom moves camera in wrong direction
• Context menu triggered on mouse release after a zoom action

I'm trying to debug -> Incorrect mouse anchor point.

[codecov]

Codecov Report

Merging #295 (bb14e9a) into main (653b0fb) will increase coverage by 0.11%.
The diff coverage is 46.03%.

@@            Coverage Diff             @@
##             main     #295      +/-   ##
==========================================
+ Coverage   65.31%   65.42%   +0.11%     
==========================================
  Files          32       32              
  Lines        4621     4686      +65     
==========================================
+ Hits         3018     3066      +48     
- Misses       1603     1620      +17     

Impacted Files	Coverage Δ
include/ignition/gui/GuiEvents.hh	100.00% <ø> (ø)
...interactive_view_control/InteractiveViewControl.cc	16.52% <10.71%> (+2.24%)	⬆️
src/plugins/minimal_scene/MinimalScene.cc	58.92% <32.75%> (-0.54%)	⬇️
src/Conversions.cc	95.00% <78.94%> (-5.00%)	⬇️
src/GuiEvents.cc	100.00% <100.00%> (ø)
src/plugins/scene3d/Scene3D.cc	48.83% <100.00%> (-0.07%)	⬇️

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[jennuine]

This looks good to me, some minor comments/questions