LCD delay improvements

[mark9064]

• No longer spins the CPU when the display task is waiting
• Unnecessary waits removed
• Sleep in - sleep out minimum interval now respected

This all assumes the datasheet is correct :P It could definitely be inconsistent in places
I'd appreciate if it at least one reviewer could check that they interpret the datasheet the same way
https://wiki.pine64.org/images/5/54/ST7789V_v1.6.pdf
See pages 48, 49, 163, 182, 184

Split from #1869

[github-actions]

Build size and comparison to main:

Section	Size	Difference
text	377528B	48B
data	940B	0B
bss	63548B	8B

[mark9064]

(InfiniSim PR now ready)

[JF002]

LGTM!
I can't remember why I added those delays in St7789::ColMod(), St7789::DisplayInversionOn(), St7789::NormalModeOn() and a few other methods. It seems to work fine without them (and I trust you made those changes according to the data sheet anyway :) ).