Implement CRSF spec for TYPE_FOLDER

[ajjjjjjjj]

• remember only first and last child id,
• load only between first and last child id,
• skip querying folder items for root folder,

Closes #461

[ajjjjjjjj]

I have tested on standard TX and RX, seems to work fine and adds noticeable speedup especially for lower pocket rates.

@wimalopaan, would you mind - i know you have some non standard CRSF devices that may be good to test this with for loading speedup and possible regressions.

[wimalopaan]

I have tested on standard TX and RX, seems to work fine and adds noticeable speedup especially for lower pocket rates.

@wimalopaan, would you mind - i know you have some non standard CRSF devices that may be good to test this with for loading speedup and possible regressions.

Very cool!
Will try that asap, but that'll happen not before the next weekend ...

[wimalopaan]

I justed this successfully! Very good.

Although I did not test that with a LA attached, I have the impression, that the tree of parameters is queried in a depth-first manner instead of a breadth-first manner.
Also, if a subfolder is opened (queried) it looks that the sibling folders are also queried, although they are not visible.

So, in general it looks that TBS agent is still faster an more efficient because only the visible folder elements are queried. Clearly, this is only possible, if the devices stick to the TBS specs for foldern containing the IDs of the children.

https://github.com/tbs-fpv/tbs-crsf-spec/blob/main/crsf.md#0x28-parameter-ping-devices

Maybe there is still some room for optimization.