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 (Could someone check if this is indeed new and not a setting I have forgotten...)

Groups:

• Explained new workflow

closes #9802 closes #9803