[change] public SensorComponent fields to properties, add custom editor

[chriselion]

Proposed change(s)

For both CameraSensorComponent and RenderTextureSensorComponent:

• Move fields to private
• Add properties for the fields (public get, usually internal set)
• CustomEditors

Useful links (Github issues, JIRA tickets, ML-Agents forum threads etc.)

Types of change(s)

• Bug fix
• New feature
• Code refactor
• Breaking change
• Documentation update
• Other (please describe)

Checklist

• Added tests that prove my fix is effective or that my feature works
• Updated the changelog (if applicable)
• Updated the documentation (if applicable)
• Updated the migration guide (if applicable)

Other comments

[vincentpierre]

I think it would make more sense to store "m_SensorName" and such in private const in case they are used somewhere else.

[chriselion]

Sorry, not quite sure what you mean. The user needs to assign a unique name to each sensor so that we can sort them deterministically, so the name here can't be const.

[surfnerd]

i think he means the string, make it a variable.

[chriselion]

Here or in the component? We currently only use them in one place, and it's kinda redundant because of reflection.

We could do something like this:
https://stackoverflow.com/a/33059272/224264
although to use nameof we'd need to make the fields internal.

[vincentpierre]

If we only use it here, I think it is fine.

[vincentpierre]

I do not think it is useful to check for changes is nothing happens when something changed

[chriselion]

Revised based on feedback from @awjuliani - the Camera and compression type can now be changed during runtime (since they don't affect the observation shape).

[vincentpierre]

You can do that ?!
Should we try to be consistent and make it the same way everywhere?

[chriselion]

I did a simple find-and-replace for the ones for HideInInspector+ SerializeField+ FormerlySerializedAs. That's as much effort as I want to put into it for this PR.