ctznooze's mashup of EZlanding, iterm_leak, and improved yaw feedforward

[ctzsnooze]

This is a 'mashup' build for testing only; its the code I fly day to day at present.

It includes:

• PR #13488, my EZLanding alternative PR based on PID input error limiting, with auto-disarm
• PR #13574, leaky iTerm on yaw
• PR #13576, yaw feedforward improvements (for 4.6)
• PR #13506, itermWindup refactoring, constraining iTerm per-axis based on pidSum

For more info, read the details of each PR. The EzLanding and EzDisarm options can be changed via the OSD.

There are two new CLI parameters at this point:

• ez_landing_disarm_threshold, which is in the OSD as well. 100 will disarm on a good bounce or impact, but not normally. A lower value will disarm more readily on landing. The disarm threshold is much higher than GPS rescue, and is only active when throttle is zero and sticks centred. If set to zero, it is disabled.
• iterm_leak this leaks yaw iTerm towards zero, and is disabled when set to 0. It isn't needed, I think, with the feedforward code, but it is put in this mashup for ongoing testing.

I'll keep it up to date and will hack the unit tests so you can flash it.

The EZLanding code probably doesn't stabilise landings as well as master,

The external functions do not use ITCM memory, so the PR doesn't exceed ITCM on F7's.

[github-actions[bot]]

Do you want to test this code? You can flash it directly from Betaflight Configurator:

• Simply put #13575 (this pull request number) in the Select commit field of the Configurator firmware flasher tab (you need to Enable expert mode, Show release candidates and Development).

WARNING: It may be unstable. Use only for testing!