[Companion] Show custom control names throughout the UI (& internal refactoring) (#4693)

* [Companion] Introduce new Boards class to further consolidate hardware metadata and remove some globals.

* [Companion] * RawSource::toString() and RawSwitch::toString() can now return custom hardware names (if given a GeneralSettings object) for the following types (respectively):
    SOURCE_TYPE_STICK, SOURCE_TYPE_SWITCH, SWITCH_TYPE_SWITCH, & SWITCH_TYPE_MULTIPOS_POT;
* RawSource::isPot() and isSlider() can now return their own index position in potConfig[]/sliderConfig[];
* Switch indicator strings can be localized if necessary.

* [Companion] Refactor model printers to use new RawSource/RawSwitch capabilities; Simplify model-to-printer mapping scheme in multimodelprinter; Use const ModelData pointer.

* [Companion] Refactor how RawSource and RawSwitch selection combo boxes are populated, using cache-able data models instead of direct manipulation; Refactor some other Helpers function into their own namespace.

* Cosmetics & forgotten qualifier.

companion/src/storage/storage.cpp

@@ -124,7 +124,7 @@ bool convertEEprom(const QString & sourceEEprom, const QString & destinationEEpr
   if (!storage.load(*radioData))
     return false;
 
-  QByteArray eeprom(EESIZE_MAX, 0);
+  QByteArray eeprom(Boards::getEEpromSize(Board::BOARD_UNKNOWN), 0);
   int size = getCurrentEEpromInterface()->save((uint8_t *)eeprom.data(), *radioData, version, variant);
   if (size == 0) {
     return false;