sensors split rc_update into new standalone module

[dagar]

This PR splits the rc update handling (rc_update) out of the sensors module monolith, similar to #13073 and #12601.

In isolation this change isn't that interesting, although it likely removes a bit of latency in RC updates and has some potential side benefits for truly RC-less systems. The larger goal is to reduce the sensors module complexity and get to the point where it's not a bottleneck for running multiple estimators. By splitting these logical pieces into separate modules they become a bit easier to manage and refactor.

A follow up PR could update this new module to properly use module parameters.

[dakejahl]

Looks good to me

[dagar]

The new module could probably use a better name. Any suggestions?

[mcsauder]

The new module could probably use a better name. Any suggestions?

### Description
The rc_update module handles RC channel mapping: read the raw input channels (`input_rc`),
then apply the calibration, map the RC channels to the configured channels & mode switches,
low-pass filter, and then publish as `rc_channels` and `manual_control_setpoint`.

Here are a few thoughts to throw at the wall, nothing I am completely in love with either though: RCSignalMapper, RCSignalHandler, RCInputHandler, RCHandler

[jorge789]

Tested on PixRacer V4:
Modes Tested

Position Mode: Good.
Altitude Mode: Good.
Stabilized Mode: Good.
Mission Plan Mode (Automated): Good.
RTL: Good.

- Procedure
Arm and Takeoff in position mode, after flying for approximately one minute, switched to altitude then stabilized mode proceed to switch to mission plan mode then make sure that vehicle follows all waypoints as shown in QGC, once completed all waypoint activate RTL vehicle landed smooth and disarmed.

Notes:
No issues noted good flight in general.

Log: https://review.px4.io/plot_app?log=b0dfe561-655a-4c14-8471-8fb52849151c

[Junkim3DR]

Tested on NXP FMUK66 v3

Modes Tested
Position Mode: Good.
Altitude Mode: Good.
Stabilized Mode: Good.
Mission Plan Mode (Automated): Good.
RTL: Good.

Procedure
Arm and Takeoff in position mode, after flying for approximately one minute, switched to altitude then stabilized mode proceed to switch to mission plan mode then make sure that vehicle follows all waypoints as shown in QGC, once completed all waypoint activate RTL vehicle landed smooth and disarmed.

Notes:
No issues noted good flight in general.

Log: https://review.px4.io/plot_app?log=cd0c9fda-cd66-47c7-97ad-a93e19fbecee

Tested on Pixhawk Pro v4

Modes Tested
Position Mode: Good.
Altitude Mode: Good.
Stabilized Mode: Good.
Mission Plan Mode (Automated): Good.
RTL: Good.

Procedure
Arm and Takeoff in position mode, after flying for approximately one minute, switched to altitude then stabilized mode proceed to switch to mission plan mode then make sure that vehicle follows all waypoints as shown in QGC, once completed all waypoint activate RTL vehicle landed smooth and disarmed.

Notes:
No issues noted good flight in general.

Log: https://review.px4.io/plot_app?log=c100d678-ee95-4aa3-8897-9fa0e559f0d0

[Tony3dr]

Tested on Pixhawk 4 V5

Modes Tested
Position Mode: Good.
Altitude Mode: Good.
Stabilized Mode: Good.
Mission Plan Mode (Automated): Good.
RTL: Good.

Procedure
Arm and Takeoff in position mode, after flying for approximately one minute, switched to altitude then stabilized mode proceed to switch to mission plan mode then make sure that vehicle follows all waypoints as shown in QGC, once completed all waypoint activate RTL vehicle landed smooth and vehicle disarmed.

Notes:
No issues noted good flight in general.

Log: https://review.px4.io/plot_app?log=4621e90d-6903-46e2-8def-ba8f8d3f06c0&fbclid=IwAR2iF5xcbaaPBK0TnLx42SnC-9EWpwZblnTHSNKJgXm9nf4q36xXL-WsbHI

[dagar]

Thanks for the review and testing. This will be easy to rename and refactor as a standalone module.