[Keyboard] Refactor handwired/splittest to support multiple boards (#6373)

* Refactor splittest to support multiple dev boards

* Refactor splittest to support multiple dev boards - revert change to number of RGB led

* Refactor splittest to support multiple dev boards - update docs

* Refactor splittest to support multiple dev boards - correct docs

* Refactor splittest to support multiple dev boards - update teensy master logic

keyboards/handwired/splittest/readme.md

@@ -4,7 +4,10 @@ Split Tester
 A two-switch tester built using two Pro Micros, mainly intended to test RGB on split keyboards. Seen here: https://www.instagram.com/p/BvCPNzynwrV/
 
 Keyboard Maintainer: [Bakingpy/nooges](https://github.com/nooges)  
-Hardware Supported: Pro Micro   
+Hardware Supported: Pro Micro, Teensy 2.0  
+Hardware Availability: 
+
+**See each individual board for pin infomation**
 
 Make example for this keyboard (after setting up your build environment):
 
@@ -15,12 +18,3 @@ Example of flashing this keyboard:
     make handwired/splittest:default:avrdude
 
 See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).
-
-Wiring
-------
-- Add switches to both Pro Micros across B3 and B6 pins
-- Add pull-up resistor to left side between VCC and F6
-- Add pull-down resistors to right side between GND and F6
-- Connect the following pins on both sides together: D0, D1, GND, VCC
-- Add I2C 4.7kOhm resistors between D0 and VCC, and D1 and VCC
-- Wire Di of RGB strip for each half to D2