display: Create Interfaces for text displays

[gsexton]

This creates a set of interfaces for use by text oriented displays like LCDs. Ultimately, I'm planning on adding multiple backpacks for hd44780, the Sparkfun SerLCD, MatrixOrbital LK204-7T, Adafruit USB LCD backpack (compatible w/ MatrixOrbital), and an SSH1106 OLED.

The arch for the backpacks will be a backpack that accepts a gpio.Group(). Then, I'll have implementations (MCP23008, 8574T, gpioioctl.LineSet, and sets of GPIO pins.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 169 lines in your changes missing coverage. Please review.

Project coverage is 93.7%. Comparing base (1a89f8f) to head (a849c37).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
display/displaytest/text.go	0.0%	169 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main     #42     +/-   ##
=======================================
- Coverage   97.9%   93.7%   -4.2%     
=======================================
  Files         33      34      +1     
  Lines       3760    3930    +170     
=======================================
+ Hits        3680    3681      +1     
- Misses        75     244    +169     
  Partials       5       5             

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[maruel]

One proposal for the argument interactive -> pauseTime but I don't have a strong opinion.

[maruel]

Thanks!