Update structure support

[tal5]

Requested on Discord.

Changes

• Deprecated LocationTag.find.structure[<type>].within[<#.#>] and LocationTag.find.unexplored_structure[<type>].within[<#.#>] in favor of LocationTag.find_structure on 1.19+.
• Deprecated server.structure_types in favor of server.structures on 1.19+.
• oldStructureTypes deprecation warning, for server.structure_types.
• findStructureTags deprecation warning, for the LocationTag.find.structure tags.

Additions

• Structure lookups language doc, detailing some edge-cases/issues with structure lookups.
• LocationTag.find_structure[structure=<structure>;radius=<number>(;unexplored=<true/{false}>)] - does a structure lookup.
• LocationTag.find_structure_type[type=<type>;radius=<number>(;unexplored=<true/{false}>)] - does a structure lookup by structure type (e.g. jigsaw structures).

[!NOTE] The old deprecated Spigot API for structures was called StructureTypes, and used server.structure_types as the tag to list them, which is now also deprecated. The issue is that there are actual structure types now, which should have their own listing tag; can probably name it ...structure_categories or something, but that's a bit dumb. It's almost all the same values as the deprecated structure_types tag, but obviously that's still a breaking change. We could not have a listing tag for these now? they're probably not as important as the actual structures which do have a listing tag - let me know what do you think.

[!NOTE] Added the 2 deprecations as SlowWarning instead of FutureWarning, as the API behind them is already (and has been) deprecated in Spigot, and provides inaccurate/missing information. Can make it FutureWarning and bump once 1.19 is the minimum supported version? but they already only show up on 1.19+, so made sense to always show a proper warning for something that's actively inaccurate & deprecated.

[mcmonkey4eva]

Is the new tag 1.19+ only? If so, it should be limited/marked as such. If it's not, the deprecations shouldn't be limited.

[tal5]

Is the new tag 1.19+ only? If so, it should be limited/marked as such. If it's not, the deprecations shouldn't be limited.

They're all already in if (isAtLeast(1.19)) checks - added 1.19+ notes to the meta deprecations though