fix #292387 : [MusicXML] Drumset of MusicXML sounds pitch

[AntonioBL]

Resolves: https://musescore.org/en/node/292387

This PR sets the channel bank to 128 before setting the first instrument, which is then added to the masterScore midiMapping (and the channel is cloned to midiMapping articulation channel).
Bank 128 is thus set for both the masterChannel and the articulation channel inside midiMapping

• I signed CLA
• I made sure the code in the PR follows the coding rules
• I made sure the code compiles on my machine
• I made sure there are no unnecessary changes in the code
• I made sure the title of the PR reflects the core meaning of the issue you are solving
• I made sure the commit message(s) contain a description and answer the question "Why do those changes fix that particular issue?" or "Why are those changes really necessary as improvements?"
• I made sure the commit message title starts with "fix #424242:" if there is a related issue
• [N/A] I created the test (mtest, vtest, script test) to verify the changes I made

[AntonioBL]

@dmitrio95 : Sorry to disturb you, but you are the expert of the midiMapping; can you please have a look at the related comment https://musescore.org/en/node/292387#comment-1042795 ?

Additional note: I think the line

MuseScore/mu4/importexport/internal/musicxml/importmxmlpass2.cpp

Line 513 in 28f7e1e

part->instrument()->channel(0)->setBank(128);

becomes redundant with the change of this PR, but I am not 100% sure.

[dmitrio95]

This doesn't seem to be an issue for this pull request, but part->setMidiProgram() also sets bank to a value which is 0 by default:

MuseScore/libmscore/part.h

Line 108 in 4983887

void setMidiProgram(int, int bank = 0);

So with this PR updatePartWithInstrument effectively sets the channel's bank to 128, adds the channel to MIDI mapping (via setMidiChannel()) and then sets the channel's bank value back to 0. Here it doesn't seem to cause any issues (although it doesn't seem right anyway), but in other places (for example, in OVE import) it might cause undesirable results. So maybe setMidiProgram() behavior should be somehow reconsidered, although this certainly doesn't belong to this PR.

[AntonioBL]

Thank you very much for your comment.

So line part->instrument()->channel(0)->setBank(128); is not actually redundant, in the end.