Rename the FuelRegistry.Builder#featureSet field to enabledFeatures

[haykam821]

This field contains currently enabled features as opposed to being a more generic feature set, so the more specific terminology already used within Yarn should be used. The arguments indirectly passed into the builder's constructor already use the terminology:

// In the ClientPlayNetworkHandler constructor
this.fuelRegistry = FuelRegistry.createDefault(connectionState.receivedRegistries(), this.enabledFeatures);

// In the ClientPlayNetworkHandler#onSynchronizeTags method
this.fuelRegistry = FuelRegistry.createDefault(this.combinedDynamicRegistries, this.enabledFeatures);

// In the MinecraftServer constructor and MinecraftServer#reloadResources method
this.fuelRegistry = FuelRegistry.createDefault(this.combinedDynamicRegistries.getCombinedRegistryManager(), this.saveProperties.getEnabledFeatures());

The names of intermediate parameters have been changed as well.