Implement random map script playerbase function.
Unifies 54 variants of the rmgen playerbase code, fixes #4805.

Add retry loops to prevent collisions of starting resources, fixes #4600 and
resources placed outside of the map area, fixes #4796.

Lays the foundation to test for collisions with Iberian walls, refs #2192 and
allows to rearrange the starting resources on all random maps without being confronted with code.

Delete remains of misc.js, leaving the rmgen files sorted by logic, fixes #4804.
Concludes what was started in rP18816, rP19282, specifically the 82 rmgen commits starting rP20115, rP20301.
Uses vector algebra, refs #4845.
Removes many Math proxy calls, refs #4933.
Removes 35 unused elevation and 24 unused cliffRadius variables, demonstrating the copy&paste antipattern.
Reduce iberian-wall hardcoding to one line, refs #4940.