DAS plugins: Support configurable severity
This introduces a concept of a "configured severity," based on the
design at https://github.com/dart-lang/sdk/issues/57034, such that
an analysis rule can be configured in analysis options to be one of:
"disable," "enable," "info," "warning," or "error."
We actually don't have any validation of what is inside a plugin
section in analysis options; that should come next.
Closes https://github.com/dart-lang/sdk/issues/59644
Change-Id: I56f1f51ef01adee7e6c042d8df9a974e7e5a11a8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/443003
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Sam Rawlins
c1c62259e7