Remove dead code (#11082)

Removed:
- MessageStore::addFromPacket and addFromString, superseded by
  tryAddFromPacket
- GeoCoord rangeRadiansToMeters, distanceTo, bearingTo
- Router::rawSend, declared virtual with no override and no caller
- ContentHandler handleHotspot, handleFs, handleAdminSettings,
  handleAdminSettingsApply, handleDeleteFsContent and their commented
  route registrations, plus the now unreachable htmlDeleteDir and the
  handleUpdateFs declaration that had no definition
- ContentHelper replaceAll
- OnScreenKeyboardModule popup chain: showPopup, clearPopup, drawPopup,
  drawPopupOverlay and their state, unreachable since the frame based UI
  was replaced by baseUI
- DebugRenderer drawDebugInfoTrampoline, drawDebugInfoSettingsTrampoline
  and the orphaned drawFrameSettings
- NodeListRenderer calculateMaxScroll, drawColumns and a stale extern
  haveGlyphs declaration with no definition
- UIRenderer::haveGlyphs, Screen::blink,
  NotificationRenderer::showKeyboardMessagePopupWithTitle,
  VirtualKeyboard::getInputText
- InkHUD touchNavLeft, touchNavRight, Applet::getActiveNodeCount,
  ThreadedMessageApplet::saveMessagesToFlash
- TwoButton::setHandlerUp, TwoButtonExtended setHandlerUp,
  setJoystickDownHandlers, setJoystickUpHandlers
- CannedMessageModule LaunchRepeatDestination, isCharInputAllowed,
  hasMessages
- TrafficManagementModule resetStats, recordRouterHopPreserved,
  saturatingIncrement
- UnitConversions::MetersPerSecondToMilesPerHour
- EncryptedStorage getSessionRemainingSeconds
- BMI270Sensor::writeRegisters, GPS::hasFlow, FSCommon copyFile,
  SerialConsole consolePrintf, buzz playLongPressLeadUp,
  memGet displayPercentHeapFree

src/modules/Telemetry/UnitConversions.cpp

@@ -10,11 +10,6 @@ float UnitConversions::MetersPerSecondToKnots(float metersPerSecond)
     return metersPerSecond * 1.94384;
 }
 
-float UnitConversions::MetersPerSecondToMilesPerHour(float metersPerSecond)
-{
-    return metersPerSecond * 2.23694;
-}
-
 float UnitConversions::HectoPascalToInchesOfMercury(float hectoPascal)
 {
     return hectoPascal * 0.029529983071445;

src/modules/Telemetry/UnitConversions.h

@@ -7,7 +7,6 @@ class UnitConversions
   public:
     static float CelsiusToFahrenheit(float celsius);
     static float MetersPerSecondToKnots(float metersPerSecond);
-    static float MetersPerSecondToMilesPerHour(float metersPerSecond);
     static float HectoPascalToInchesOfMercury(float hectoPascal);
 
     // Bound a float before Arduino String(float) renders it: its fixed char[33] + dtostrf overflow