Add table showing complexity of methods for Input

[ShadowMitia]

Objective

Fixes #10106

Adds a table showing computational complexity, as seen for Query (and similar to std::collections docs).

Solution

Add the complexity table

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Changelog

• Add complexity table for Input methods

[ShadowMitia]

I've added information on all methods, hope this is ok.

I've tried analyzing the source and I've also used the std::collections doc on performance also as a reference.

I'm not completely sure on the values for just_pressed/just_released/pressed, which all have a call to contain.
I'm kind of assuming it is comparable to a get complexity as seen in the collections docs.

[alice-i-cecile]

Nits on the wording, but nothing blocking. All of the listed time complexities appear correct to me.

[ShadowMitia]

Updated with all suggestions and rebased on latest changes.
I still think the clear method should be documented as O(n), unless there is a good reason not to 😄
Should be good to go otherwise!