Startup behaviour fixes (#1306)

* Reduce PPS max to 20V to avoid instability

Some PSU's cant actually run at 21V

* Creating a rough draft of a "pre start check" concept

* Newer alpine

* Cleaning up MHP detection

* Cleanup comments

* PID: Run prestart based on ADC IRQ rather than times

* MHP30: Far better startup for detecting tip gain

* Newer alpine for github CI

source/Core/BSP/BSP.h

@@ -86,6 +86,10 @@ enum StatusLED {
 };
 void setStatusLED(const enum StatusLED state);
 
+// preStartChecks are run until they return 0
+// By the PID, after each ADC sample comes in
+// For example, on the MHP30 this is used to figure out the resistance of the hotplate
+uint8_t preStartChecks();
 #ifdef __cplusplus
 }
 #endif