Move all 3D non viewport layout menu options from the view menu to the perspective menu

[ryevdokimov]

Describe the project you are working on

The Godot Editor

Describe the problem or limitation you are having in your project

These menus mix and duplicate similar functionality which is a little disorganized in my opinion. Some shortcuts end up being duplicated as well.

Note the unbound shortcut is for an individual viewport:

Describe the feature / enhancement and how it helps to overcome the problem or limitation

The view menu will end up looking like this, and only things relating to the layout of editor viewports will be added here in the future.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

There are already PRs that have been merged or opened to move some of that functionality for example: godotengine/godot#100435

Gizmo visibility should also be configurable on a per-viewport basis (possibly a separate yet related proposal).

This should continue until they're fully separated. If someone wants some viewport specific settings to apply globally, options to copy/paste settings between viewports or add a "Apply selected viewport settings to all viewports" could be added.

If this enhancement will not be used often, can it be worked around with a few lines of script?

No.

Is there a reason why this should be core and not an add-on in the asset library?

This is core.