Standardize usage of compound words, and document standards in docs style guide

[tetrapod00]

Your Godot version:
4.4
Issue description:
There are some compound words, like "antialiasing", that appear in the docs in both hyphenated form "anti-aliasing" and in single-word form "antialiasing". For consistent style, we should choose one form and standardize.

Some examples:

• antialiasing / anti-aliasing
• runtime / run-time
• screen space / screen-space
• builtin / built-in / built in (this one depends on context)

This is a fairly low priority issue. We should not break translations just to change this. However, we should choose which form to use for each compound word, document that choice in the style guide, and change existing usages whenever other changes are being made.

There's also precedent in #3502, #6978 of applying changes like this all at once.

URL to the documentation page (if already existing):
The whole manual and class reference.