Provide guidance for misconfigured config

[stuartmorgan-g]

The first time I tried to import an unnamed enum it took a while, because I hadn't realized it was a different config entry, and I tried various attempts with both enum and global before finding the right part of the docs. In general, it's tricky to debug a mistake because failures are basically silent, and can be caused by lots of different things (wrong element type, typo, wrong header, etc.)

Of course we can't figure out every problem at runtime, but I wonder if we could add some simple heuristics to give feedback. E.g.,:

• For globals, enums, and unnamed-enums, if an inclusion or exclusion doesn't match anything, try it with the other two types and if it would match something that way, print a message suggesting that it may be in the wrong place.
• Keep track of any symbol within a Hamming distance of one or two of a non-wildcarded pattern of the same type, and if that list is non-empty and that pattern didn't match anything, suggest that it may be a typo and print the close value(s)

[liamappelbe]

The best place to insert this logic would be to modify the DeclarationFilters class so that each of its methods count matches (or maybe add a DeclarationFiltersMixin that the subtypes of DeclarationFilters can use).