Allow excluding traits from auto-completion

[GyrosOfWar]

Some crates (e.g.owo_colors) have traits that add a bunch of methods to every type (e.g. OwoColorize). This can pollute the auto-completions for types quite a lot. An example for a type from aws_sdk_s3 in VSCode:

I looked for existing issues and found #7449, which would help, but it would be nice to have a more granular way to do this. I also wouldn't be opposed to try my hand at implementing this myself, but it'd be cool if someone could assess whether this is a feasible issue for a beginner in this codebase (like myself).

[lnicola]

I think this has a bunch of dupes, including #17477 and possibly others.

[lnicola]

Closing as a duplicate of #17477