[FEATURE] Add dedicated sensor manager.

[Milotrince]

Description

Add SensorManager to Simulator. Sensor classes can now have per-scene multi-sensor caching.

Related Issue

Rigid Tactile Sensors #1451 will be rebased on this PR.
IMU Sensor Milotrince#1 is also based on this PR. (I can't do a "stacked PR" directly in Genesis repo since my branch doesn't live there, which is why the PR currently lives in my fork of Genesis)

Motivation and Context

The current sensor implementation does not allow for caching across multiple sensors, and usage is un-Genesis-like (unintuitive, e.g. does not align with add_camera pattern). See new IMU for an implementation/usage example.

How Has This Been / Can This Be Tested?

Will add tests per sensor.

Checklist:

• I read the CONTRIBUTING document.
• I followed the Submitting Code Changes section of CONTRIBUTING document.
• I tagged the title correctly (including BUG FIX/FEATURE/MISC/BREAKING)
• I updated the documentation accordingly or no change is needed.
• I tested my changes and added instructions on how to test it for reviewers.

[Milotrince]

Some design decisions made:

1. Why have a SensorManager?

Typically in a scene, a robot may have multiple of the same type of sensor. Previously the implementation tried to cache sensor data at the class level, but this will not work when running multiple scenes. The SensorManager is owned by Simulator and thus can operate at the per-scene, per-sensor-type level. It can also automatically update all sensors (see below)

2. Why does SensorManager need to updated all sensors at step() instead of computing values at read?

For time delay and other types of noise, we will need to buffer the history. So either users will have to call step themselves (or otherwise face unintended/inaccurate values), or we can cleanly handle this inside of the simulator step (more aligned to Genesis's usage design).

3. Why is read() now handled at the base Sensor?

For future contributions of new sensors, we want to enforce usage of the cross-batch, cross-sensor-type caching mechanism to ensure high sensor performance in Genesis.

[Milotrince]

looks like unit test failed because of camera