Add Protobuf and OpenCV to CI preinstalls

[ferdnyc]

Make sure our CI runs are built with OpenCV and Protocol Buffers enabled.

[codecov]

Codecov Report

Merging #626 (af98221) into develop (47afa20) will decrease coverage by 0.90%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #626      +/-   ##
===========================================
- Coverage    52.79%   51.89%   -0.91%     
===========================================
  Files          130      151      +21     
  Lines        10882    12341    +1459     
===========================================
+ Hits          5745     6404     +659     
- Misses        5137     5937     +800     

Impacted Files	Coverage Δ
src/effects/ObjectDetection.cpp	0.00% <ø> (ø)
src/effects/Stabilizer.cpp	0.00% <ø> (ø)
src/effects/Tracker.cpp	0.00% <ø> (ø)
src/EffectInfo.cpp	0.00% <0.00%> (ø)
tests/Frame_Tests.cpp	100.00% <0.00%> (ø)
src/sort_filter/KalmanTracker.h	100.00% <0.00%> (ø)
src/CVObjectDetection.h	0.00% <0.00%> (ø)
tests/CVTracker_Tests.cpp	100.00% <0.00%> (ø)
src/ProcessingController.h	40.54% <0.00%> (ø)
src/CVTracker.h	81.81% <0.00%> (ø)
... and 18 more

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[ferdnyc]

From an apt perspective, the added installs are:

sudo apt install libopencv-dev libprotobuf-dev protobuf-compiler

(Leave out that last one, you'll get very strange errors because instead of being replaced with the path to the protoc executable, the protobuf::protoc target ends up in the Makefile as a dependency. Which breaks it completely, :: not being valid unescaped path characters in Make.)

Installing individual OpenCV library components (e.g. libopencv-core-dev, etc. is a nice idea, to avoid installation bloat, and that's how I started. But none of them install the CMake configs needed to properly configure the targets. Those are only in libopencv-dev itself. So it'll just have to install everything.