Add keyboard shortcuts to the project manager
Add keyboard shortcuts to the project manager

- Ctrl + N: New Project
- Ctrl + I: Import Project
- Ctrl + S: Scan for Projects
- Ctrl + E: Edit Project
- Ctrl + R: Run Project
- F2: Rename Project
- Delete: Remove Project
  - Already implemented previously, but moved to use `ED_SHORTCUT()`.

Note that depsite using `ED_SHORTCUT()`, these shortcuts won't appear
in the Editor Settings' Shortcuts dialog and won't be remappable since
the project manager code isn't run in the editor.

(cherry picked from commit 9bda49e03014549370074ac52a3b7bac1d421c86)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot