[Sensor] Fisheye and Equirectangular semantic sensors

[bigbike]

Motivation and Context

This diff does the following stuffs:

• developed 2 new sensors: fisheye semantic sensor, and equirectangular semantic sensor;
• developed new visualization functionality to visualize the semantic info from the aforementioned sensors;
• added demos in the utility viewer (We chose parameters for "GoPro" in our demo);
• small fixes;

The results are as follows:

How Has This Been Tested

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[Skylion007]

@bigbike This ended up being a bit more involved so I added the tests myself.

[erikwijmans]

@bigbike @Skylion007 looks like this is going to revert #1222 ?

[Skylion007]

@erikwijmans Fixed.

@bigbike Your changes reminded me that the SensorSpec has a channels property that weren't setting with Python or Habitat-Lab so I tried to update the example to set it. Interestingly, whenever I see it to 3 channels it crashes.

[bigbike]

@bigbike Your changes reminded me that the SensorSpec has a channels property that weren't setting with Python or Habitat-Lab so I tried to update the example to set it. Interestingly, whenever I see it to 3 channels it crashes.

This is because the default value for channel should be 4 not 3 because there is an alpha channel. See here:
https://github.com/facebookresearch/habitat-sim/blob/master/src/esp/sensor/VisualSensor.h#L35-L38

[Skylion007]

LGTM: Let's merge.

[Skylion007]

@bigbike It all passed except for that flakey codecov upload.

[bigbike]

@Skylion007 : I re-ran the CI. It passed all the tests. Now it is ready to be committed. THANK YOU very much for contributing to this big PR as well! I sincerely appreciate it.

Merge it in.