Add swap army and swap artifacts to the heroes meeting screen

[zenseii]

This PR adds the swap army button and swap artifacts features to the heroes meeting screen.

Relates to #4084

Button design by @FlorianBaba and me.

Swap artifacts was added to make the screen design more consistent and it has been requested by the community according to @Branikolog.

Rotation of the arrow parts was done with this ( sin270 = -1 and cos270 = 0): https://en.m.wikipedia.org/wiki/Rotation_matrix

[github-actions]

⚠️ Clang-Tidy found issue(s) with the introduced code (1/1)

[Branikolog]

Hi, @zenseii
I've checked the PR.
Visually everything looks nice and absolutely naturally, as from design point.
I've noticed, that there's no pressed state for artifact swap button (there's no pressing animation for this only button).

[oleg-derevenetz]

Hi @zenseii I added an assertion to verify that hero will not get an empty army due to army exchange and also modernized some army-related code (while I'm here).

[zenseii]

Thanks, @oleg-derevenetz!

[Districh-ru]

Well done, @zenseii!
I have one suggestion that can be addressed in a new PR:
We should add the right-click info to help players fully understand the mechanics of all arrow-buttons in this dialog.

[zenseii]

Well done, @zenseii! I have one suggestion that can be addressed in a new PR: We should add the right-click info to help players fully understand the mechanics of all arrow-buttons in this dialog.

Thanks, @Districh-ru! Yes, this is a good suggestion. We can make such a PR after this one.

[ihhub]

@zenseii , huge thanks for implementing this!