Implement "Flip direction" shortcut action for new dynamics & hairpins

[avvvvve]

The 'X' keyboard shortcut which triggers the "Flip direction" action doesn't work for cycling through above/below position of dynamics and hairpins in #22662.

It should do the following:

1. If Position is set to Below, pressing X switches Position to Above
2. If Position is set to Above, pressing X switches Position to Below
3. If Position is set to Auto...
   • And the object is below the staff, pressing X switches Position to Above
   • And the object is above the staff, pressing X switches Position to Below

You won't be able to set Position back to Auto using the X shortcut. The shortcut should have no bearing on "Center between staves".

Logging now to not hold up merging #22662!