Make longhorn analyzer configurable from analyzer specs.

[xavpaice]

Problem to solve

The Longhorn analyzer is currently hardcoded and not configurable via a support-bundle spec. it's output is also fairly limited in just stating weather longhorn is "healthy" or "unhealthy"

We've had reason to inspect longhorn for more intricate details like the number of volume replicas or more fine-grained information about the setup but the analyzer doesn't allow for this without code changes.

Definition of done:

• The necessary changes are merged to the troubleshoot repo
• Running the above analyzer against a support bundle in Vendor Portal identifies the issue (if a collector is needed you may have to ask a customer to run the spec and upload it)
• The analyzer provides an explanation on how to resolve the issue for the user, linking to any additional information that might be needed to fix the issue.

[xavpaice]

https://app.shortcut.com/replicated/story/55128/make-longhorn-analyzer-configurable-from-analyzer-specs

[xavpaice]

https://github.com/longhorn/longhorn/issues/2118#issuecomment-748099002 has an example of how to collect a bundle for making an upstream Longhorn bundle, which is likely to provide more detailed info for analysis