Add "Copy As..." core submenu to editor context and Edit titlebar menu

[joaomoreno]

We want to have a core editor/context/copy menu so extensions can contribute menu items to a Copy As... context menu. We want the menu available in the titlebar Edit menu as well.

We want the submenu to render only if it has items inside. This is the default behavior already implemented in the editor context menu. But it wasn't for the titlebar menu. I spent nearly half an hour looking for the right places to make the titlebar menu behave the same way. I found out that we duplicate code not only between the usual menu world and the titlebar world but even between native and custom titlebars... (see both menubarControl.ts files changed) We have so much different code that translates menus into something usable, and none are easy to find. Could we please have a debt item to clean all of this up @bpasero and @sbatten?

Adding @jrieken as well for review, for an API eye.

Fixes #118208

cc @alexr00 and @eamodio for adoption once this gets merged in

[bpasero]

Yielding to @sbatten to review this and follow up on the debt side of things. I believe we should have a "Copy As" also in the file explorer as I remember @egamma expressing some interest in making that menu smaller for all the copy entries we have.

[sbatten]

@joaomoreno please verify with native menus on windows or linux as well

[joaomoreno]

Pushed changes which differentiate between editor context and titlebar edit, introduced menuBar/edit/copy menu id.