Refactor WaveformFactory and Pref

[acolombier]

• Make WaveformWidgetFactory::findHandle* const and use something like

  auto it = std::find_if(m_waveformWidgetHandles.cbegin(), m_waveformWidgetHandles.cend(), [type](const auto& handle){   return handle.m_type == type; }); return it == m_waveformWidgetHandles.cend() ? -1 :   std::distance(m_waveformWidgetHandles.cbegin(), m_waveformWidgetHandles.cend());
  

• Replace raw pointer in WaveformWidgetFactory::create[*]Waveform with smart pointers
• Use templated UserConfig functions whenever applicable and replace verbose set or get with setValue or getValue
• Assessing the situation with WaveformWidgetAbstractHandle and aim to remove it if possible
• Use a model in the preference for waveform types, and allow sorting by most to least recommended, instead of alphabetically
• Refactor src/waveform/widgets/waveformwidgettype.h to adopt a similar style than in Refactor/preferences enums #12798

This is a dependency for #13226

[acolombier]

@Swiftb0y let me know if you would like me to take a look at this if you are happy with doing the clean up yourself

[Swiftb0y]

I'm currently ringing for time a little so I don't know if I have the time. I'll try to whip up something later today, If not feel free to take over.

[Swiftb0y]

@acolombier so I spent the day and came up with https://github.com/Swiftb0y/mixxx/tree/refactor/gh13245-waveform-factory%26prefs (doesn't fully build; also currently segfaults on teardown because of 424b1c9 which I haven't found the time to dig into).
I'll try to finish that tomorrow.

[acolombier]

Great! Thanks for your effort.