MusicXML note head "filled" element not imported or exported

Steps:
1a- load attached file. Some note heads are not filled and some of the 1/2 notes have filled note heads; this information is lost in the import.

1b- The same happens if a note head type of a 1/4 note is set to half in the inspector and the score is then exported to MusicXML: the "filled" property is not set.

See also: #90736: Import tremolos between two notes from Finale MusicXML

Possible PR:
https://github.com/musescore/MuseScore/pull/2336