various fix for slurs, slurs no more possible between linked staves and staves in different parts
fix #23083: Pasting tie or slur causes crash
fix #23126: Slur of pasted notes ends on note it was copied from
fix reordering of instruments corrupts spanner
fix #23125: Slurs of existing instrument disappear after removing top instrument
fix #21721: Spanners not properly deleted when corresponding anchoring notes are deleted
fix spanner ticks when removing measures and undo
fix #23131: crash on deletion of selection that includes last measure of score
fix #23129: chordnames not propagated to parts if parts generated after score load
implement up/down keys to move anchor for slurs
allow slurs from higher track to lower