lexgen update (#495)
As a temporary hack, just skip the `com.atproto.temp.importRepo`
endpoint which uses Lexicon features that lexgen does not support.
There are a small number of actual lexicon updates, but the main
motivation here is to handle *all* of the `didDoc` and `plcOp` fields.
That is also a hack for now, but this resolves a number of regressions,
eg with refreshSession.