[Core] Allow custom timings for WS2812 PIO driver

[KarlK90]

Description

Allows setting of custom WS2812 timings using the defines found in ws2812.h, it also uses these timings as it's default now. Furthermore the reset timing is now applied correctly before starting a new transfer. Due to implementation details the waiting times are rounded to 50ns intervals.

WS2812 default timings

Period	Time
WS2812_T1H	900ns
WS2812_T1L	350ns
WS2812_T0H	350ns
WS2812_T0L	900ns
RESET	280us

T1H + T1L

T0H + T0L

Reset

SK6812 timings

Period	Time
WS2812_T1H	500ns
WS2812_T1L	450ns
WS2812_T0H	400ns
WS2812_T0L	750ns
RESET	80us

T1H + T1L

T0H + T0L

Reset

Deviation from 80us due to the driver choosing the longer T0H + T0L or T1H + T1L period which is irregular in this case.

Types of Changes

• [x] Core
• [x] Bugfix
• [x] New feature
• [x] Enhancement/optimization
• [ ] Keyboard (addition or update)
• [ ] Keymap/layout/userspace (addition or update)
• [x] Documentation

Issues Fixed or Closed by This PR

Checklist

• [x] My code follows the code style of this project: C, Python
• [x] I have read the PR Checklist document and have made the appropriate changes.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[KarlK90]

CC: @xyzz @jepler

[jepler]

Yay ARRAY_SIZE

[KarlK90]

@sigprof If you happen to have some spare time I would like your opinion on this implementation :slightly_smiling_face:

[KarlK90]

Tested and running stable since ~2 months on my RP2040 keyboard