[Refactor] Simplify UnmarshalJSON with Dedicated Handlers

[haitwang-cloud]

This PR refactors the UnmarshalJSON method for ReplicatedDevices to improve code clarity and structure. Key changes include:

• Modularization: Created separate handlers (handleStringInput, handleNumericInput, handleListInput) for different input types, enhancing readability and simplifying future maintenance.

• Robust Error Handling: Enhanced the error handling in handleListInput to allow processing of list elements independently.

• Code Refactoring: Eliminated redundancy by centralizing error checking logic.

• Generics Readiness: Prepared handleNumericInput for future adaptation to Go's generics (once available).

[haitwang-cloud]

@klueska PTAL

[haitwang-cloud]

Upon reviewing, I identified a bug in the previous submission that resulted in the failure of two existing unit test functions. To address this, I've removed the switch statement, which was causing the issue.

Here are the current unit test results:

(base) ➜  v1 git:(main) ✗ go test ./...                          
ok      github.com/NVIDIA/k8s-device-plugin/api/config/v1       0.634s

[haitwang-cloud]

Ping @klueska

[haitwang-cloud]

Ping @elezar

[github-actions[bot]]

This PR is stale because it has been open 90 days with no activity. This PR will be closed in 30 days unless new comments are made or the stale label is removed.