[Documentation] Mention complexity for container operations

Issue originally raised by artem.sokolovskii 

We have the algorithmic complexity section in the general Container Classes page.

But this approach has several drawbacks:

• This page is not easily discoverable
• It does not mention all operations (no removal)
• It's not very convenient to jump to this page every time you need to check a specific method

The cppreference documentation for container operations usually has the "Complexity" section (eg. https://en.cppreference.com/w/cpp/container/list/insert)
We should probably add something similar to individual functions, or at least at class documentation level.