Add support for using Safety switch pins on IOMCU to control ProfiLEDs via bit banging

[bugobliterator]

• CPU time cost is minimal, only upto 7us per call is consumed.
• Flash and Data Cost is as follows:

Before:

BUILD SUMMARY
Build directory: /home/sidbh/Programming/ardupilot-chibios/build/iomcu-f103-dshot
Target                   Text (B)  Data (B)  BSS (B)  Total Flash Used (B)  Free Flash (B)  External Flash Used (B)
-------------------------------------------------------------------------------------------------------------------
bin/iofirmware_lowpolh      52404      1196    19300                 53600            7836  Not Applicable
bin/iofirmware_highpolh     52404      1196    19300                 53600            7836  Not Applicable

After

BUILD SUMMARY
Build directory: /home/sidbh/Programming/ardupilot-chibios/build/iomcu-f103-dshot
Target                   Text (B)  Data (B)  BSS (B)  Total Flash Used (B)  Free Flash (B)  External Flash Used (B)

-------------------------------------------------------------------------------------------------------------------
bin/iofirmware_lowpolh      52160      1196    19296                 53356            8084  Not Applicable
bin/iofirmware_highpolh     52160      1196    19296                 53356            8084  Not Applicable

[tridge]

for the ccache failure, I think we need to change it to be two other H7 boards we test, maybe Pixhawk6X and ZeroOneX6 ?

[tridge]

hmm, the ccache test (see test_ccache.yml) uses Durandal-bdshot and Pixhawk6X, which should be unaffected by this PR, which implies this PR is changing something it shouldn't

[peterbarker]

Ping @bugobliterator - those plane trips have to be good for something? :-)

[peterbarker]

Board                    AP_Periph  blimp  bootloader  copter  heli  iofirmware  plane  rover  sub
CubeBlack                           776    *           776     776               776    776    776
CubeOrange-periph-heavy  408                                                                   
CubeOrangePlus                      784    *           784     776               784    776    776
CubeRedPrimary                      *      *           *       *                 *      *      *
Durandal                            *      *           *       *                 *      *      *
Hitec-Airspeed           *                                                                     
KakuteH7-bdshot                     *      *           *       *                 *      *      *
MatekF405                           *      *           *       *                 *      *      *
Pixhawk1-1M-bdshot                  *                  *       *                 *      *      *
f103-QiotekPeriph        *                                                                     
f303-Universal           *                                                                     
iomcu                                                                *                         
revo-mini                           *      *           *       *                 *      *      *
skyviper-journey                                       *                                       
skyviper-v2450                                         *                                       

[tridge]

i'd say that using the safety pin like this offends my sensibilities a bit, but holding my nose I will merge