Fix #91571, fix #114366 again, and other menu updates

[IsaacWeiss]

Second round of menu changes, again mostly discussed on the forums previously.

• Page View, Continuous View, and Single Page View added to View menu
• Toolbars submenu added to View menu with toolbar toggles and Customize Toolbars
• Zoom In and Out moved to Zoom submenu, with Zoom to 100% added
• Documents Side by Side and Documents Stacked renamed to Split View Left/Right and Split View Top/Bottom
• Insert Pitch commands added to Add > Notes menu
• Delete and Remove (Timewise Delete) added to Edit menu
• Regroup Rhythms (Reset Note and Rest Groupings) added to Tools menu
• Remove (Timewise Delete) added to context menu for barlines, measures, notes and rests
• Load Style removed from context menu for canvas

Still to do, needing advice (though none block this from merging and being useful):

• Check the appropriate layout mode entry in the View menu on score load
• Add Insert Rest command (per https://musescore.org/en/node/126986), some commented out lines already added in preparation
• Disable Delete and Remove in Edit menu when they’re not applicable

[lasconic]

Documents Side by Side and Documents Stacked renamed to Split View Left/Right and Split View Top/Bottom

Why? Where is the discussion? I remember we choose this name after some discussion and checking other software: https://musescore.org/en/node/3542
It would be great if you don't change stuff in a single PR without previous discussion to avoid discussion like https://musescore.org/en/node/120676

So I would prefer a single PR to address each item, after a discussion. Even if it's a short one.

[IsaacWeiss]

@lasconic:
As I just mentioned in a comment on the (closed for good reason) #2804, I unfortunately sometimes fail to make a note of where I found ideas. I did read https://musescore.org/en/node/3542 (perhaps around the time that the names of the vertical/horizontal/column/row page view/layout/scrolling setting was under discussion), but I didn't comment on it at the time; and I may be the only one who has a problem with the "Documents" wording, and opening a PR without prior discussion was bad form.

Should I close this and start again from the beginning, one thing at a time?

[lasconic]

If you think something is not controversial, you can do a PR. Changing wording is always controversial though... The insertions and deletions in menus looks good. Adding WIP commented code is not good, make a new PR if you need help putting something together. Hope it makes sense.

[IsaacWeiss]

Split View question asked at https://musescore.org/en/node/3542.