Allow flag-based blacklisting and whitelisting of overmap locations on a per-region basis

[ralreegorganon]

Summary

SUMMARY: Infrastructure "Allow flag-based blacklisting and whitelisting of overmap locations on a per-region basis"

Purpose of change

Provides a JSON-based mechanism that allows overmap locations to be blacklisted and whitelisted on a per-region basis based on the flags that those locations have. This will let regions exclude and include certain location types without the locations themselves having to opt in and out of every region.

It allows mods that attempt to suppress certain types of locations to more cleanly specify their intent, e.g. specifying a flag as blacklisted rather than doing a copy-from for every overmap special they want to exclude and updating its occurrences to 0 (though that path is still available if a single instance needs to be excluded while retaining others of a similar class).

Describe the solution

Added new section to the regional map settings which allows for operations based on the flags that overmap features have, and the code to load these settings.

Initially supports a whitelist and blacklist such that features with matching flags are either excluded (blacklist) or exclusively used (whitelist) during overmap generation.

Updated overmap special placement to evaluate these lists when building the default batches of overmap specials for placement. Hard coded terrain placements were not adjusted in this initial pass, as generally speaking the hardcoded placements of features are a bit less open to external modification via JSON and more tightly coupled to their placement algorithms. Any overmap-based placement routine can read these settings and be updated to use them, however.

Updated the No_Fungi, No_Anthills, No_Beehives, and No_Triffids mods to use this mechanism for blacklisting locations rather than copying overmap_special entries and overriding the occurrences values.

Update the REGION_SETTINGS and JSON_FLAGS documentation.

Describe alternatives you've considered

We could make new sections in the regional settings for specifying allowed overmap terrains and specials directly by id, as is currently done for the locations that make up cities, but I don't particularly care for that since it makes it more difficult for new content to be included, must be manually maintained when there are changes, and misses out on the flag part of this that allows operating on a broad range of features just based on common attributes.

[ZhilkinSerg]

Great change. A huge step to move CLASSIC_ZOMBIES from world options into a mod.