[controller] LVMLogicalVolumeSnapshots

[astef]

Description

Refactoring

• split different controllers into packages
• make controllers structs and put external services there
• make controllers functions/methods private
• move hard-coded test data into a file, and embed it
• rename some "Run*" methods to "New*" functions, since they are not running, but creating things
• resource reconcilation code no longer depends on "sigs.k8s.io/controller-runtime/pkg/*" packages, it will be easy to migrate to a newer version of it
• block device reconciler is now called "discoverer", to comply with existing naming strategy
• extracted "resource clients" - kubectl client methods, which are used in different places
• constants are separated (LLV used "Failed" status from LVG sometimes)

Bugfix

• call to UpdateLVGConditionIfNeeded used old "Success" condition string, fixed to "Applied"
• GetAPIBlockDevices was called from different controllers, but generated logs with the same, invalid controller name
• LVG status.thinPools[*].usedSize in reported 100x more space used then it really was

Enhancement

• added LVMLogicalVolumeSnapshot reconciler, which creates/deletes snapshot volumes
• updated LLV reconciler to handle "clones" and "restores" - new LLV resources with spec.source set.

Checklist

• [x ] Documentation updated according to the changes.
• [ x] Changes were tested in the Kubernetes cluster manually.