nRF52840 Power Management Stage 1 (Boot Lock) - v2.3 preparation work

This commit lays some of the ground work for the upcoming power management fix that allows users to configure the boot lock behaviour.

It is *not* the full fix yet. The goal is to break up the larger commit into smaller chunks so it is easier to review and softer to merge.

Improvements:
- MainBoard: Add bool to check if power management has been initialised (later to be consumed by CommonCLI to validate we can safely configure the settings)
- MainBoard: Add bool to validate LPCOMP is supported on the board (gates LPCOMP config so it doesnt wedge on an unsupported board)
- NRF52Board: Rename initPowerMgr() -> pwrmgtInit() to align with the "pwrmgt" prefix being used by any power management related functions in the upcoming new version
- NRF52Board: Add a shutdown reason for "None" so the `get pwrmgt.bootreason` command doesnt erroneously return "Unknown"
- NRF52Board: Add gate in configureVoltageWake to not arm LPCOMP when power management isn't initialised or the board doesn't support LPCOMP (i.e. we havent defined the AIN pin)
- NRF52Board: Reference the LPCOMP AIN pin directly instead of from the per-board definitions to align to the upcoming deprecation of the per-board static configs
- NRF52Board: Drop LPCOMP hysteresis as it broadens the wake voltage too much and makes the board less likely to self-recover
- NRF52Board: Separate LPCOMP and VBUS wake arm into their own functions

src/helpers/NRF52Board.h

@@ -25,15 +25,15 @@ struct PowerMgtConfig {
 #endif
 
 class NRF52Board : public mesh::MainBoard {
-#ifdef NRF52_POWER_MANAGEMENT
-  void initPowerMgr();
-#endif
+private:
+  bool pwrmgt_initialised = false;
 
 protected:
   uint8_t startup_reason;
   char *ota_name;
 
 #ifdef NRF52_POWER_MANAGEMENT
+  void pwrmgtInit();
   uint32_t reset_reason;              // RESETREAS register value
   uint8_t shutdown_reason;            // GPREGRET value (why we entered last SYSTEMOFF)
   uint16_t boot_voltage_mv;           // Battery voltage at boot (millivolts)
@@ -41,6 +41,7 @@ protected:
   bool checkBootVoltage(const PowerMgtConfig* config);
   void enterSystemOff(uint8_t reason);
   void configureVoltageWake(uint8_t ain_channel, uint8_t refsel);
+  void pwrmgtWakeArmVbus();
   virtual void initiateShutdown(uint8_t reason);
 #endif
 
@@ -63,6 +64,10 @@ public:
   uint8_t getShutdownReason() const override { return shutdown_reason; }
   const char* getResetReasonString(uint32_t reason) override;
   const char* getShutdownReasonString(uint8_t reason) override;
+  bool isPwrMgtInitialised() const override { return pwrmgt_initialised; }
+  #ifdef PWRMGT_LPCOMP_AIN
+    bool getWakeLpcompSupported() const override { return true; }
+  #endif
 #endif
 };