* Loosen thresholds for gyro consistency check until temperature compensated units are the norm
  * Cut down string lengths so they make it through the MAVLink transport as a whole

This change makes the mixer load and reset operation closer to thread-safe. It was guarded one-way before and in only one location. This change ensures that its being locked out from both directions. The accesses to the locking variables still need work because they are non-atomic.

This change makes the operation more robust as it flags the whole group invalid in the first step. This should not be confused with being thread-safe - to be thread-safe, all accesses to _first and the following linked list need to be guarded by a mutex. This should be done outside of the mixer in the driver though, as the method depends on the board architecture.

UAVCAN: Make GPS module use the multi-topic facility so that a normal GPS and an UAVCAN GPS can co-exist and do not write on top of each other.

NuttX had the CRTSCTS define incorrectly set for only output flow control, which broke our flow control logic. This commit patches NuttX and puts in addition a guard in place to prevent any future issue with the non-POSIX define being incorrect.

This has been debugged and identified by @ecmnet, which was the main contribution for this patch.

This patch fixes two issues:
  * It sends the message on the first call, making sure that the first update gets sent out.
  * It improves the rate scheduling. In an experiment with 0.5, 50 and 250 Hz all rates were correct within 0.3% of the intended rate.

The transition state reporting was inverted because of a typo. Code analysis suggests this will only have an effect in manual transition.

The rotor count was incorrect which meant that control surfaces like elevons were scaled incorrectly. This was the main reason for really bad SITL performance

Its sufficient to use sqrtf() with floating point resolution and its better to use the Matrix library call for local and global position yaw

The VTOL status reporting and the mission status reporting were both suboptimal. VTOL was too slow, mission reporting too fast

The main changes include:
 * Better attitude tuning for airframes (more realistic models, the models had previously not as much thrust as the real vehicles)
 * Better waypoint and navigation default parameters which match the on-hardware parameters
 * More suitable minimum and trim airspeeds for VTOL and fixed wing which prevents stalls that happened in SITL previously (the new airspeeds match the real vehicles nicely)

  This was the cause of the CI failure on the hot fix

   This hot fix essentialy revert commit 265af481209d60033f7cd4c4216048b1ce3eb435
   in NuttX/nuttx. The commit STM32 serial: Make input hardware flow-control work with RX DMA.
   From Jussi Kivilinna has broken the DMA on an STM32F4 in a yet TBD way.
   The symptoms are lost data on RX, the DMA count decrements but
   the data ia not written to memory. This looks to be introduced but the
   non circular DMA settings.

* Set LPE FUSE for standard iris sitl config.

* Relax fault detection handling.

* Always correct lidar.

   This allows a ICM20xxxx with an unkown product ID to be used
   with the mpu6000 driver.

   This change will issues a warning for any part with an unknown product ID.
   For mpu6000 parts (-T 6000 or not specified) it will then exit.
   For any ICM20xxxx part with an unknown product ID it will accept the ID
   and run with it.

   N.B. This fix expecte the value in the product ID register to be
   a per chip constant. (Not changing during operations)