typing: add some type hints to fastannotate that have decayed in the last year Somewhere since 10db46e128d4, `_knownopts` decayed to `set` for unknown reasons. Also, `annotateopts.default` changed from bytes to str. While that is correct, I noticed that PyCharm was flagging the member fields as undefined in `shortstr()`, so add those to keep it happy. (There are no complaints from pytype because that module is excluded, due to the missing reference to `linelog.copyfrom()` that I'm not sure how to fix.)