This PR modifies the verification cache to be detector type-aware by adding the detector type to the cache keys. There is also a slight change to the key generation logic to prevent it from reslicing the passed-in Raw value. (We haven't seen any trouble from this so far, but I think it's good to disarm the footgun while I'm here.)
When adding tests, I also realized that the existing tests were inconsistently named, so I cleaned them up.
This resolves#3984.
This PR introduces a cache that allows the scanner to avoid emitting multiple requests to verify the same credential. In practice, it doesn't seem to reduce scan time at all, but it does seem to reduce the number of calls to FromData rather drastically.
The cache is implemented as an opt-out feature that can be disabled with a new CLI flag. If we don't like this, we can change it.
The metrics collection hopefully isn't too architecture-astronauty; I wanted to create something useful here that could also accommodate future Prometheus configuration without making the implementation all stupid.
Cody Rose