The ConsoleLinkForExpression() function now escapes console URLs in such a way
that works both in emails and in HTML.
Change-Id: I917bae0b526cbbac28ccd2a4ec3c5ac03ee4c647
This includes required refactorings to enable replacing the http client (for
testing) and moving the NotificationReq type definitions to the "notifications"
package, so that this package doesn't need to depend on "rules" anymore and
that it can instead use a representation of the required data which only
includes the necessary fields.
This commit adds telemetry for the Prometheus expression rule
evaluator, which will enable meta-Prometheus monitoring of customers
to ensure that no instance is falling behind in answering routine
queries.
A few other sundry simplifications are introduced, too.
