Allow black/whitelisting scenarios

[anothersimulacrum]

Summary

SUMMARY: Infrastructure "Add scenario whitelist/blacklist capability"

Purpose of change

@I-am-Erk wanted this for Cataclysm: Dark Days of the Dead

Describe the solution

In the character selection menu, skip displaying a scenario if it has been blacklisted.
Add struct scen_blacklist, containing a std::set of the ids of blacklisted scenarios, and a bool whitelist.
Add member functions for loading and finalizing this blacklist.
Create a file-global instance of this struct in scenario.cpp, and use it as the loaded blacklist.
Add scenario::scen_is_blacklisted() that checks if the scenario is on that blacklist.

Describe alternatives you've considered

Making whitelists and blacklists separate, but I felt that was unecessary, and this is functional.

Testing

Create a mod with this as the modinfo.json, and switch the subtype between whitelist and blacklist.

[
  {
    "type": "MOD_INFO",
    "ident": "scenmod",
    "name": "No scenarios!",
    "authors": [ "anothersimulacrum" ],
    "maintainers": [ "you" ],
    "description": "Tests scenario blacklists",
    "dependencies": [ "dda" ]
  },
  {
    "type": "SCENARIO_BLACKLIST",
    "subtype": "whitelist",
    "scenarios": [ "largebuilding" ]
  }
]