analyzer: ErrorFilterOptionValidator improvements
analyzer: ErrorFilterOptionValidator improvements

* error codes are static and final; no need for a public getter
* lint codes are `late final` because they may be registered up until the
  options are validated; the field is lazily calculated at such time.

Change-Id: I8d9c1e9ab4d69be77be49b44f62e605c3f06fd2e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/192561
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Reviewed-by: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@google.com>
Commit-Queue: Samuel Rawlins <5cf2cac5eec2ad6d0eb2b0f4ff6af9a590ce2bf6@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk