Blacklist for weapon targetting instead of whitelist only (noTargetCategory)

Currently we only have whitelisting for weapon targeting. onlyTargetCategory and badTargetCategory. A blacklist would be far more useful and require less tapdancing for gamedevs in order to set up proper categories for weapon targets. For games that don't use armor systems it isn't a huge issue, but for games that do, categories becomes a nightmare to deal with if you want to set them up well.

Addition of goodTargetCategory would be champ, but that's just me dreaming :-D

https://springrts.com/phpbb/viewtopic.php?f=21&t=29769

Start by locating the existing handling for onlyTargetCategory and badTargetCategory, then read the linked forum discussion for the intended targeting semantics. Done means the engine supports the requested blacklist behavior through noTargetCategory and the existing targeting behavior remains covered by relevant tests, if present.

Written by the indexing model from the issue text.