Fix wrong direction of broken beam segment in longer-dotted note + shorter note groups
Simpler tests; improved comments
Fix #19472

Implements [Left] / [Right] not only from notes/chord-rests but from any element whose parent is a note, a chord-rest or a segment
For elements attached to segments, move to the chord/rest in element track, if it exists
regression test fix
safeguard GUI against addPitch() returning 0
 #17906 (Using MIDI input to input chords causes crash): Reworked moveToNextInput() logic in addPitch(). moveToNextInput() is called before actually inserting a new node, except if adding to a chord or if it is the first note inserted. A new flag InputState::moveBeforeAdding has been added just for this purpuse.
fix #17906: when a chord is detected on MIDI input, the cursor is moved back before adding each subsequent note after the first, so that all of them become part of the same chord at the same position; the 'active' variable in MuseScore::midiNoteReceived() is used in a comparison, instead of directly as a parameter, since sometimes it can be -1
use QXmlStreamReader for xml parsing
fix #19306 : Elements of instruments added after creation not positioned correctly
Update libmscore/system.cpp
Search box/filter added to the instrument list
fix #19687 : moving bracket causes crash
Fix #19374

Wide (two-digit) numbers in TAB collide; fixed
Separated Note::tabHeadWidth() and Note::tabHeadHeight() methods for TAB's from generic Note::headWidth() and Note::headHeight()
enable musicxml support, move needed xml functions to musicxml code
fix all regressions detected by mtest
complete switch to QXmlStreamReader
fix reading of session xml file
#16057: basic MusicXML export of chord diagrams