Mention complexity of functions if it is known

[mamekoro]

I was looking for information on the performance of Query and found the following comment.

Query.get is O(1), and resources are also a constant time lookup :)
― #6556 (comment)

What about other functions?

I frequently use query-like functions such as Query::get(), Query::single(), Commands::entity(), Res<Input<KeyCode>>::just_pressed(), etc, but I'm just a Bevy user and don't know about the complexity of them.

If the complexity of a function is known, please consider documenting it.

[alice-i-cecile]

This is a great idea :) Going to convert it to a discussion for now: feel free to open as many issues as you'd like for specific APIs / clusters of APIs. Otherwise this issue will stay open in a state of limbo forever, as this isn't exactly "completable" in its current forms.

[mamekoro]

Thanks, I'll open a new issue.