Fix #20931 - State of Inspector widget was not remembered across MuseScore sessions

Fixed by:
*) Storing in the settings the state of the Inspector widget (dock state, position, size) at close down
*) Unconditionally creating the Inspector widget at srt up (as for the F9 palette widget) before settings is read
*) Restoring the Inspector state from settings at start up
fix #20456: Measure number not displayed if top staff is hidden
Merge pull request #322 from mgavioli/Fix_20931_remember_inspector_status

Fix #20931 - Remember state of Inspector widget
fix crash when palette width is too small
extend timesig creation in master palette with note groups dialog
fix #20942: Changing font from Emmentaler to Gonville doesn't update time signature
fix #20943
fix crash in timesig properties dialog
Implements persistent state of piano keyboard (PianoTools class)

*) PianoTools is unconditionally created at startup (like palette and inspector), so that saveState() and restoreState() can manage it
*) Shown/hidden state is stored into / read from QSettings
fix #20954: Brackets drawn incorrectly in Gonville
update note groups dialog
Merge pull request #327 from mgavioli/PianoKeyboard_persistent_state

Piano Keyboard: persistent state
remove playpanel dependency from sequencer
fix aeolus installation
Merge pull request #323 from lvinken/20581-capx-impl-3

20581 capx impl 3
fix #20880
fix sequencer setPos()
another try in fixing the seq
fix #20892
prevent zero slur crash