Refactor EInkDisplay (#3299)

* Refactor EInkDisplay
A lot of variant specific code is merged, with the macros pushed to the respective variant.h files.
"Dynamic Partial" code has been purged, pending a rewrite.

* fix: declare class only if USE_EINK, init all members

* refactor: move macros to platformio.ini
Responds to https://github.com/meshtastic/firmware/pull/3299#issuecomment-1966425926

* fix: EInkDisplay::connect() references old macros
Usage was in a block of variant-specific code, which had been intentionally left untouched.

* fix: remove duplicate macros from variant.h

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

variants/MakePython_nRF52840_eink/platformio.ini

@@ -10,5 +10,8 @@ lib_deps =
   ${nrf52840_base.lib_deps}
   https://github.com/meshtastic/ESP32_Codec2.git#633326c78ac251c059ab3a8c430fcdf25b41672f
   zinggjm/GxEPD2@^1.4.9
+  -DEINK_DISPLAY_MODEL=GxEPD2_290_T5D
+  -DEINK_WIDTH=296
+  -DEINK_HEIGHT=128
 debug_tool = jlink
 ;upload_port = /dev/ttyACM4