Add default keyboard shortcuts to various actions in the 3D editor

[Calinou]

• Follow-up to https://github.com/godotengine/godot/pull/93578 (can be merged independently).

This also changes the 2D editor Toggle Grid shortcut to match the 3D editor one. (Out of curiosity, is Ctrl + Apostrophe standard for toggling grids in any app? If so, we can readd it as an alternative second shortcut in both the 2D and 3D editors.)

New shortcuts:

• Ctrl + E: View Environment
• Ctrl + I: View Gizmos
• Ctrl + Shift + I: View Grid
• Ctrl + F: View Information
• Ctrl + Shift + F: View Frame Time
• Ctrl + U: Half Resolution
• Numpad 0: Cinematic Preview
  • Note that if using Emulate Numpad, the shortcut won't work to leave the cinematic preview due to https://github.com/godotengine/godot/issues/93677.
    • Fixed by https://github.com/godotengine/godot/pull/93724.

In both the 2D and 3D editors, this shortcut was also added:

• Ctrl + #: Configure Snap

Edit: Cinematic Preview shortcut was changed from Ctrl + Alt + R to Numpad 0 to match Blender. I'd like to make Focus Selection support Numpad Period to match Blender, but it doesn't seem to work for some reason, regardless of the Emulate Numpad editor setting (I'm testing with a physical numpad).