HsIdParseErrors should not have an ErrorKind

The following discussion from !2246 (merged) should be addressed:

• @Diziet started a discussion: (+3 comments)

  I don't think this impl is correct, really. We can't know what the cause is unless we know the source of the data. So I think we should probably defer assigning a kind to a higher level that knows whether this should be (for example) InvalidConfig.