RC_Channel: added RC_SWITCH_TYPE parameter

[tridge]

this makes setting up the flight mode switch on the widely used OpenTX
radios with 6 mode buttons much easier. Setting RC_SWITCH_TYPE=1 changes the flight mode 6 pos thresholds to be correct for the OpenTX 6 pos switch

[IamPete1]

Why not a bit in options? Unless we add support for more than 6 modes via this param I cant see us wanting any more than two options so we should be OK as a single bit.

[tridge]

Why not a bit in options? Unless we add support for more than 6 modes via this param I cant see us wanting any more than two options so we should be OK as a single bit.

I think we're likely to have other mappings of PWM to flight modes in the future, which makes an enum make sense.
I also would like to add support for more than 6 modes, and this would be the key param to do that. For example, 9 modes using 2 3pos switches, or 12 modes using a 6pos switch and another switch.

[rmackay9]

This looks OK to me.

Re the suggestion of adding more than 6 flight modes through a combination of switches, I'll throw in my regular editorial on this which is that we already support 6 modes on a single switch and additional modes can be triggered from auxiliary switches.

I think attempting to add support for more and more flight modes adds complexity which leads to user error and the real problem is the very limited interface of these classic transmitters (e.g. those without a built in GCS). The proper solution is to replace the transmitter with a Herelink (or similar) or add a GCS which provides so much more feedback and features.

[IamPete1]

I would prefer to take the opportunity to move to a RCx_OPTION. We could then have FlightMode as a option and FlightMode OpenTX. Then we can do FlightMode 9 and FlightMode A + FlightMode B for mixing or whatever in the future.

I can see that this might back us into a corner where we have to add FLTMODE_CH2 ect

But the concept of supporting different mappings is a good one, we have several issues requesting more than 6 channels.