[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/flasheepromdialog.cpp

@@ -227,7 +227,7 @@ void FlashEEpromDialog::on_burnButton_clicked()
   if (patch) {
     QString filename = generateProcessUniqueTempFileName("temp.bin");
     QFile file(filename);
-    uint8_t *eeprom = (uint8_t*)malloc(getEEpromSize(getCurrentBoard()));
+    uint8_t *eeprom = (uint8_t*)malloc(Boards::getEEpromSize(getCurrentBoard()));
     int eeprom_size = getCurrentEEpromInterface()->save(eeprom, *radioData, 0, getCurrentFirmware()->getVariantNumber());
     if (eeprom_size == 0) {
       return;