Improve autocompletion with get_node

[HolonProduction]

Fixes #73638
Fixes #73164
Fixes #82592
Fixes (partially) #78860

by prioritizing annotated types over get_node. Also adds the script of the node if no type is annotated. Currently the sorting does seem broken with SCRIPT type though and the members won't show up at the top (#85239 should fix the sorting problem).

Through adding the script to the type this also
Fixes #82258

[YuriSizov]

Hey, this needs a rebase against the up-to-date master.

[HolonProduction]

Done

[adamscott]

Solid PR. Fixes a lot of paper cuts with the GDScript editor.

[akien-mga]

Thanks!

[YuriSizov]

Cherry-picked for 4.2.1.

[Henrique-Henrique]

Is it intentional for it to only work in the class body?

[HolonProduction]

When resolving the type of a subscript access we call two different methods. One is meant to deduct the type of a get_node call on the the node which the script is attached to. This PR fixes this method to don't do this if the type is annotated.

If this method does not resolve a get_node call we try again with a more general purpose method to deduct the type of an identifier, icon_scope or icon in your case.

This method has the issue of always using the type of the last assigned expression (which is just Node for get_node) for local variables instead of the annotated type. It is a separate issue which is addressed in #85224 or #74888.