Improve TransformUnstructured; Log GVK, type value

[tdmanv]

Change Overview

Improves TransformUnstructured

• Adds a nil check for u
• Logs the GroupdVersionKind on Serialization errors
• Types the struct as metav1.Object instead of interface{}

Pull request type

Please check the type of change your PR introduces:

• 🚧 Work in Progress
• 🌈 Refactoring (no functional changes, no api changes)
• 🐹 Trivial/Minor
• 🐛 Bugfix
• 🌻 Feature
• 🗺️ Documentation
• 🤖 Test

Test Plan

kanister/pkg/kube/snapshot/ go test -check.f TestNilUnstructured
OK: 1 passed
PASS
ok      github.com/kanisterio/kanister/pkg/kube/snapshot        0.029s

• 💪 Manual
• ⚡ Unit test
• 💚 E2E

[pavannd1]

LGTM