UI: Add scene grid mode to view menu

[cg2121]

Description

Makes toggling of the scene list grid mode also available in the view menu.

Motivation and Context

Not just in a context menu.

How Has This Been Tested?

Toggled grid mode in the view menu.

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.