Fix #18312 - ensure stem direction is updated correctly in tremolo properties pane

[wizofaus]

Resolves: #18312

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[wizofaus]

NB at least InspectorModelWithVoiceAndPositionOptions has exactly the same implementation, other models tend to check whether the changed property set contains the relevant ID, but it strikes me as premature optimisation...if anything what would seem to make more sense is to refactor all the of the property loading etc. to be handled automatically by AbstractInspectorModel (buildPropertyItem() would need to keep track of the link between property ids and the returned items etc., then loadProperties( ) could be implemented generically for all models)

[RomanPudashkin]

And it's not perfectly done in that model either. You should check if PropertyIdSet contains the required properties

[wizofaus]

Ok so can I propose as a compromise:

a) we add "loadProperties( const PropertyIdSet&, const StyleIdSet&) to AbstractInspectorModel, and the default implementation of onNotationChanged is to call this
b) all models should only have a single loadProperties( ) function (overriding the above), whereby the assumption is that if the sets are empty, then all properties should be loaded.

Because the current duplication of code seems to be highly likely to lead to unexpected behaviour in the future if one version of loadProperties( ) is updated differently from the other.

[RomanPudashkin]

Let's avoid any refactoring within the scope of this PR and only change the implementation of TremoloSettingsModel::onNotationChanged

[wizofaus]

But then you're asking me to continue the pattern of code duplication in the other models that we really should be trying to avoid. If you'd prefer to do the refactoring yourself then ok, as that will fix this issue and prevent similar future issues.