New api

[GrantM11235]

Pros

• Much faster for iterators, probably because it doesn't take a dyn Iterator anymore
• Easier to write interface drivers, no more gigantic match blocks (the parallel interface impl is about 100 lines shorter)
• No more runtime errors for unimplimented data formats
• It should work with 9-bit and 18-bit interfaces (untested)

Cons

• 8-bit Display drivers are now responsible for splitting up u16s. This only requires 1-3 lines of code
• Display drivers that support 8-bit and 16-bit interfaces are slightly more complex (only an extra 50 lines or so)

Todo

• Rename trait?
• Update comments
• Update changelog
• Write migration guide

[GrantM11235]

Update: I was able to port the top three display drivers (ssd1306, ili9341, and st7789) to this api without much difficulty

[GrantM11235]

Sorry for the force-push, I wanted to make a small change to the api.
The previous version of this PR had send_{iter,slice} methods that took a DataOrCommand enum but I realized that it is more ergonomic to just have send_{command,data}_{iter,slice} methods.