The simpler logic is more robust towards future refactoring.

Bootup failed in some cases with:
ERROR [mixer] can't reset mixers on /dev/pwm_output1

The reason was the mode change was not applied yet.

 - PWM_OUT_MAX_INSTANCES is a constant (static constexpr) not available to the preprocessor

 - skip _objects[1] access if only 1 possible instance
 - command line request new mode via atomic

This ensures that all PWM outputs get correctly inialized on targets that only support one.

Important to know if the app is running.

PX4 uses banks of 8 outputs as a logical structure. Boards that have
more outputs than 8 get multiple instances. This is an arbitrary choice
that helps with overall structure and enables the mixing of different
device classes (like FMU, IO or UAVCAN).

 - generate PWM_MAIN 1-14
 - generate PWM_AUX 1-8
 - generate PWM_EXTRA 1-8
 - px4io and pwm_out directly read configuration parameters
    - only available and active physical outputs are actually shown for configuration
 - overall saves flash despite adding many new parameters

_num_outputs is set according to the mode_pwmX call, which is required
for camera triggering.
This fixes camera triggering via PWM, as it avoids overwriting the channel.

 - add backup schedule at minimum PWM rate
 - fixes #15043

Required on durandal if camera triggering is enabled.

 - this is done to minimize real end-to-end latency
 - actual pulse width only updated for next period regardless of output module
 - add cycle interval perf counter

This reverts commit 0c8dcf94.

 - we have better motor test facilities these days

 - split out header

Chip-select and SPI initialization uses the new config, whereas the drivers
still use the existing defines.

The configuration in board_config.h can be removed after all drivers are
updated.

stm32:ToneAlarmInterfacePWM TIM15-TIM17 have a BDTR Register

common:board_crashdump Add H7 support

stm32/board_mcu_version:Support H7

PX4 ADC:Use 32 interface and resoution abstraction

Added PX4 stm32h7 ADC driver

stm32h7:adc fix ADC ready check

fmu: handle BOARD_HAS_PWM==5

cmake: improve error handling for NuttX olddefconfig failures

WorkQueueManager:Quiet loadmon stack warning

camera_trigger:GPIO support < 6 GPIO

Adjust stack sizes (under hw stack check)

PX4 System changes Supporting STM32H7 PX4IO Driver

aerotenna_ocpoc:ADC add px4_arch_adc_dn_fullcount

init.cmake:Track Upstream change needing Make.def at config time

PX4 System changes Supporting STM32H7

NuttX CMakeLists.txt Track upstream changes

Common board_crashdump add header and px4 config

NuttX simplify callinb make libapps

Use UINT32_MAX for error return

drivers:uavcannode NuttX chip is now hardware

drivers:uavcanesc NuttX chip is now hardware

px4io:Avoid Race on AP to PX4 IO upgrade

 - Astyle chokes on the module description strings, so for now we can keep them near the bottom of each file.

and remove the px4_ prefix, except for px4_config.h.

command to update includes:
for k in app.h atomic.h cli.h console_buffer.h defines.h getopt.h i2c.h init.h log.h micro_hal.h module.h module_params.h param.h param_macros.h posix.h sem.h sem.hpp shmem.h shutdown.h tasks.h time.h workqueue.h; do for i in $(grep -rl 'include <px4_'$k src platforms boards); do sed -i 's/#include <px4_'$k'/#include <px4_platform_common\/'$k/ $i; done; done
for in $(grep -rl 'include <px4_config.h' src platforms boards); do sed -i 's/#include <px4_config.h/#include <px4_platform_common\/px4_config.h'/ $i; done

Transitional headers for submodules are added (px4_{defines,log,time}.h)

Some of these perf counters were useful during initial development, but realistically aren't needed anymore, some are redundant when we can now see the average interval from `work_queue status` and some of them simply aren't worth the cost at higher rates.

mixer.cpp ensures the string is null-terminated (buffer length is 2048).

Required for pwm_out_sim: only publish actuator_outputs when we get
actuator_controls. Otherwise lockstep startup does not work.
The issue was there before but hidden, due to a long poll timeout.

Works with HIL too.

Tested with SITL + HITL

 * adds a work_queue systemcmd that will bring a tree view of all active work queues and work items
 * WorkQueues now track attached WorkItems and will shutdown when the last WorkItem is detached

And make sure fmu calls MixingOutput::updateSubscriptions on startup even
if no mixer is loaded, so that it gets scheduled.

As there is nothing pwm-specific about it.

This should be a pure refactoring, no functional change.