Various minor improvements

[oleg-derevenetz]

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This PR:

• Rewrites the Rand::Queue logic. The previous logic was weird and did many nonsense, there is a way to do the same much easier and without rewriting the contents of the queue (the whole process can be const);
• Simplifies the BagArtifacts::exchangeArtifacts(). Instead of passing bags and heroes separately, this method has been turned into static and accepts only exchanging heroes. Also a long-standing TODO has been implemented;
• A minor modernization of a code related to Army and Troop has been performed.