Reduce test skip and options to tolerate non-deterministic failure

[traversaro]

We recently have a few PRs that solved non-deterministic failures:

• Properly initialize to false ftInitialized variable #193
• Fix non-determistic reading of constant zero values for imu and laser plugin #194
• Fix robotinterface plugin crashes by closing it as soon as one of its devices is destroyed #186

Thanks to these fixes, we can reduce the number of workarounds, and only run multiple times tests that are known to be flaky.

[traversaro]

Ok, apparently CameraTest still segfaults on apt, while ConcurrentInstancesTest fails like:

ODE INTERNAL ERROR 1: assertion "!colliders_initialized" failed in dInitColliders() [collision_kernel.cpp:168]

that is due to gazebosim/gz-sim#18 .

[traversaro]

Ok, the good news is that all test pass on macos now, so #54 is fixed. On conda we still have problems with LaserTest and CameraTest, while on apt with CameraTest and ControlBoardOnMultipleGazeboInstancesTest/ConcurrentInstancesTest.

[traversaro]

Ok, now the CI passes, and in the tests we just skip/permit failure only for tests for which we have open issue tracking the problems.