add x sampling to throttle curve preview to match firmware (#4439)

* add x sampling to throttle curve preview to match firmware

* Clamp throttle value to the range [0, 1] in PID tuning initialization to avoid  senseless output

* revert previous change and clamp expothr to 0..100

* fix throttle curve preview when throttle limit is scale

* ¯\_(ツ)_/¯ AI rewrite of the  redrawThrottleCurve() function. Could not get the Throttle Limit type Clip to draw correctly. This works perfectly.

* revert control point movent to 4.5 method

* conciseify comments

Author: marc-frank