Improve TAB fretting algorithm.

An attempt to improve the current implementation to better deal with the case in forum post #29876 and possibly even with less specialized cases.

Changes:
- when a note changes of pitch, its fretting is discarded before any fretting
- each note not yet fretted is sorted for fretting as belonging to the string most convenient for it. This affects the order in which notes are evaluated during fretting.

Note: the algorithm can still be fooled by casual note entry and by changing note pitches by large intervals (octave), but it seems anyway better than before.
fix #29776: Solo is not activated on file load
fix MusicXml import of natural-flat and natural-sharp accidentals
fix import for quarter tone and three quarters tone accidentals when accidental tag is missing
fix microtonal accidentals export
fix microtonal accidentals import (e.g. from a MusicXml file exported by Sibelius 7.5)
Remove text styling from accessibility info
	modified:   libmscore/tempotext.cpp
	modified:   libmscore/text.cpp
fix #28316
	modified:   mscore/instrwidget.cpp
	modified:   mscore/instrwidget.ui
Add accessibility for instrwidget.ui
	modified:   mscore/instrwidget.ui
add more text symbols & shortcuts
fix #29981: shortcuts for key sig, time sig, & symbols palettes
fix #30071
cleanup and comments
Merge pull request #1174 from andreituicu/score_accessibility

Remove text styling from accessibility info
Merge pull request #1175 from MarcSabatella/palette-space

Add more updates for palettes & shortcuts
fix insertion of hairpins and ottava with shortcuts, fix copy paste of hairpins
fix #21257 : Breath is placed correctly when dropped on a note in other voice than default
fix some tests
Fix a potential crash in FiguredBass

In theory, `lastCR` may be null in line 1090. It should not happen in normal operations, but one never knows...
Fixes to GP3 import faults