Add lws_display and minimal example support for esp32-wrover to match wsp32-heltec-wb32
Since no usable buttons that don't affect something else on wrover kit, assumes
a button to 0V on GPIO14.
Make a start on generic peripheral and bus drivers to provide
meta-functionality regardless of platform.
On the one hand this simply provides...
- bitbang i2c on top of esp-idf gpio apis
- ssd1306 oled chip driver as found on Heltec WB32
- modifications to the minimal example test for esp32 to use that
... on the other hand, those capabilities are provided by creating:
- an abstract i2c class object
- an abstract gpio class object
- i2c class implementation using the abstract gpio for bitbang
- an abstract display class object
- an abstract display state (brightness, animated change,
on/off/init tracking, autodim after inactive, auto-off /
blanking after inactive)
... with the intention, eg, you only have to add a platform
implementation for the gpio to be able to use the i2c-based
display drivers and state handling, and i2c bitbang, without
any other modifications.
