broken mine placement on tiny maps

[mimo]

On tiny maps, if the starting angle of the mine is aligned with the cc angle, there is not available room to position the starting mine (because the cc is already quite near the border of the map), leading to very unbalanced map like the one from the command.txt attached (with r20223) with player 1 without stone. We should either exclude these angles and retry, or decrease the dist of the mine to the cc. (see for example ​https://trac.wildfiregames.com/ticket/4600#comment:7 for imposing several constraints on the starting angles).

[elexis]

In 20283:

Fix rmgen2 SimpleObject and RandomObject ignoring the 3 invalid map border tiles.
Let validT take the responsability to account for the actually valid region of map tiles instead of each caller.

Fixes #4814, refs #4636, #4796

[elexis]

The above commit is needed so that retry loops are informed that entity placements at the map border actually failed and can thus retry. The actual retry loops for all maps are coming soon.

[elexis]

In 20815:

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.