Update getting started 2D to 4.3

[Piralein]

Images:

• Update Project Settings images, because of new tab order
• Update Input Map images, because of new icons and action name reference
• Update Add Script Dialog image, because of color change
• Update Group images, because it was split into scene and global groups
  - Update Signal connect image, because it gets added with type hints
• Added image to visualize the "make unique" step for the music resource

Code:
- Added return type to all functions, because they are added by default

Groups:

• Explained new workflow

closes #9802
closes #9803

[skyace65]

@Piralein given the discussions in RocketChat could you please remove the return types from this PR so the other fixes can get merged?

[skyace65]

player_signal_connection.webp needs to be updated. it still has the -> void in it. Other than that this PR looks good!

[skyace65]

Thanks!

[mhilbrunner]

Cherry-picked to 4.3 in #10038.