extract iwTree.cpp

[morganchristiansson]

callbacks.cpp is 3293 lines in master.
I thought it makes sense to split it to smaller files.
s25client has pattern with one window per cpp file in libs/s25main/ingameWindows/ so maybe do the same here?

Was going to start with texture window but that will conflict with other open PRs so start with tree window.
discuss.

[Flamefire]

To be blunt: What is the advantage? It is just moving code around so looks like work without a benefit. Large files compile faster than many smaller ones and it works 🤷

[morganchristiansson]

Fair point.
I just think callbacks.cpp is becoming dumping ground for all UI component callbacks and it will grow as further changes are made.
s25client has very small files per window I thought it could be nicer organisation.
But after actually scrolling through callbacks.cpp I realized it's not so bad actually.