Replace slow RGB wrapper for is31fl3731 driver with a custom implementation
which double-buffers with two frames and writes pixels in batches (or all 144 in bulk).

Speeds up default RGB breath effect from ~12FPS to ~60FPS.

Fixes KMKfw#859.

Signed-off-by: Phil Howard <github@gadgetoid.com>

Speed up Keybow 2040 I2C further to ~5ms (200FPS) by increasing from the default 100KHz to 400KHz I2C.

Since Keybow 2040 does not include a Qw'St connector, we need not worry about other I2C devices.

Signed-off-by: Phil Howard <github@gadgetoid.com>

Write all 144 LED values (only 48 are used) in one transaction.

This is faster with 400KHz than trying to be smart.

Signed-off-by: Phil Howard <github@gadgetoid.com>

Speed up RGB a little more by skipping the first 17 and last few unused elements.

Signed-off-by: Phil Howard <github@gadgetoid.com>

Create the address lookup only once for a further 30% performance boost.

Co-authored-by: xs5871 <xs5871@qn-4.net>
Signed-off-by: Phil Howard <github@gadgetoid.com>

Bring references to the output buffer and address lookup into the hot path,
gives around a .7ms speedup by using optimised (local scope first) qstr lookups.

Signed-off-by: Phil Howard <github@gadgetoid.com>

Remove hot path conversion to bytes and drop double-buffering which had no visible impact.

Reduce the size of the output buffer to remove leading 17 and trailing 4 bytes, and prime
the buffer with the first LED address.

Drop offset multiply and cache LED offsets in address lookup.

Iterate through address lookup and unpack offset, r, g, b.

Update time is now ~4ms and much more stable.

Signed-off-by: Phil Howard <github@gadgetoid.com>