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- MessageStore::addFromPacket and addFromString, superseded by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/motion/BMI270Sensor.cpp

@@ -444,16 +444,6 @@ bool BMI270Sensor::writeRegister(uint8_t reg, uint8_t value)
     return wire->endTransmission() == 0;
 }
 
-bool BMI270Sensor::writeRegisters(uint8_t reg, const uint8_t *data, size_t len)
-{
-    wire->beginTransmission(deviceAddress());
-    wire->write(reg);
-    for (size_t i = 0; i < len; i++) {
-        wire->write(data[i]);
-    }
-    return wire->endTransmission() == 0;
-}
-
 uint8_t BMI270Sensor::readRegister(uint8_t reg)
 {
     wire->beginTransmission(deviceAddress());