Add support for 32 motors, including dodecahexa-octa (two-layers of 8 motors each)

[peterbarker]

This PR is a mashup of two other PRs which conflicted with one another.

tridge's PR (#27598) added 32-rotor support and a half-baked "m32" SITL frame to test it. I've completed the work on the 32-motor demo frame.

@muramura 's PR (#21157) added support for the 16-motor decahexa frame. It also modified ArduPilot to support 16 motors, which was a subset of tridge's 32-motor support, 'though remembered to patch AP_Periph to match the rest of ArduPilot.

I've reworked both sets of patches significantly to create this combined set, notably trying to bring consistency to the naming of files and frames.

Replaces #21157
Replaces #27598

Both new frames are flown in our "FlyEachFrame" test successfully.

[peterbarker]

I've removed a patch which did this:

@@ -355,7 +355,7 @@ SRV_Channels::SRV_Channels(void)
 #if NUM_SERVO_CHANNELS > 16
         if (i >= 16) {
             // default to GPIO, this disables the pin and stops logging
-            channels[i].function.set_default(SRV_Channel::k_GPIO);
+            channels[i].function.set_default(SRV_Channel::k_none);
         }
 #endif
     }

.... it was killing various autotests.

[amilcarlucas]

Binary Name      Text [B]         Data [B]     BSS (B)        Total Flash Change [B] (%)      Flash Free After PR (B)
---------------  ---------------  -----------  -------------  ----------------------------  -------------------------
arducopter-heli  -268 (-0.0147%)  0 (0.0000%)  4 (+0.0015%)   -268 (-0.0147%)                                  138324
antennatracker   124 (+0.0092%)   0 (0.0000%)  -4 (-0.0015%)  124 (+0.0092%)                                   615828
arducopter       216 (+0.0118%)   0 (0.0000%)  0 (0.0000%)    216 (+0.0118%)                                   136212
ardurover        184 (+0.0110%)   0 (0.0000%)  0 (0.0000%)    184 (+0.0110%)                                   292980
arduplane        196 (+0.0108%)   0 (0.0000%)  4 (+0.0015%)   196 (+0.0108%)                                   150148
blimp            124 (+0.0090%)   0 (0.0000%)  -4 (-0.0015%)  124 (+0.0090%)                                   593480
ardusub          516 (+0.0320%)   0 (0.0000%)  -4 (-0.0015%)  516 (+0.0319%)                                   348512

[peterbarker]

Board                    AP_Periph  blimp  bootloader  copter  heli  iofirmware  plane  rover  sub
CubeOrange-periph-heavy  24                                                                    
CubeRedPrimary                      40     *           88      40                48     56     216
Durandal                            120    *           232     -272              216    200    536
Hitec-Airspeed           *                                                                     
KakuteH7-bdshot                     16     *           64      16                24     32     120
MatekF405                           16     *           48      40                48     32     240
Pixhawk1-1M-bdshot                  16                 48      48                48     40     304
bebop                               4096               -12400  0                 -8336  0      -16576
f103-QiotekPeriph        *                                                                     
f303-Universal           *                                                                     
iomcu                                                                *                         
revo-mini                           16     *           48      48                56     40     104
skyviper-v2450                                         40