v2 needs font handling update

[cschol]

These instances of font handling need update per the v2 API. They currently cause the VST to crash.

References to fonts cannot be stored across frames in v2.

src/MentalCounters.cpp
132-
133-  NumberDisplayWidget3()
134-  {
135:    font = APP->window->loadFont(asset::plugin(pluginInstance, "res/Segment7Standard.ttf"));
136-  };
137-
138-  void draw(const DrawArgs& args) override

src/MentalMasterClock.cpp
229-
230-  NumberDisplayWidget2()
231-  {
232:    font = APP->window->loadFont(asset::plugin(pluginInstance, "res/Segment7Standard.ttf"));
233-  };
234-
235-  void draw(const DrawArgs& args) override

src/MentalKnobs.cpp
161-  std::shared_ptr<Font> font;
162-
163-  NumberDisplayWidget4() {
164:    font = APP->window->loadFont(asset::plugin(pluginInstance, "res/Segment7Standard.ttf"));
165-  };
166-
167-  void draw(const DrawArgs& args) override

src/MentalGateMaker.cpp
160-  std::shared_ptr<Font> font;
161-
162-  NumberDisplayWidget() {
163:    font = APP->window->loadFont(asset::plugin(pluginInstance, "res/Segment7Standard.ttf"));
164-  };
165-
166-  void draw(const DrawArgs& args) override