[MU3] fix #316536: Add missing baritone-horns and euphoniums to orders.xm…

[bmarwell]

…l and templates

Resolves: https://musescore.org/en/node/316536

Adds euphoniums especially to Brass Ensembles and European Concert Bands.
Just for completeness, although not too common, also to orchestral.

• 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
• I created the test (mtest, vtest, script test) to verify the changes I made

[Jojo-Schmitz]

Commit- and PR title is wrong, should be #316536
Also you have marked the conversations resolved but not submitted the requested changes

[bmarwell]

Commit- and PR title is wrong, should be #316536
Also you have marked the conversations resolved but not submitted the requested changes

Sorry, something went wrong when pushing the update (which I did not see). But as I had the commit ready (and thought I pushed it), I already resolved the conversations.

Anyway, PR is updated now.

[Jojo-Schmitz]

I wonder whether this would need to get ported to master