replaced panic() calls with proper error handling in production code

[PulkitDadwal]

What type of PR is this?

/kind bug

What this PR does / why we need it:

This PR fixes critical reliability issues by replacing panic() calls with proper error handling in production code. Previously, various components (webhook, controller-manager, status controllers, search proxy, utilities) would crash the entire application when encountering errors, leading to service unavailability. The changes ensure graceful error handling with proper logging and error returns, improving system reliability and debugging capabilities.

Which issue(s) this PR fixes:

Fixes #6657

Special notes for your reviewer:

• All panic() calls in production code have been replaced with proper error handling
• Mock/testing files were intentionally left unchanged as panic() is appropriate there
• Generated files were not modified as they should not be manually edited
• Added necessary fmt imports where error formatting was needed
• Maintained backward compatibility while improving error handling patterns

Does this PR introduce a user-facing change?:

karmada-webhook: Fixed the issue that webhook would crash on configuration errors
karmada-controller-manager: Fixed the issue that controller-manager would crash on kubernetes config errors
karmada-search: Fixed the issue that search proxy would crash on unsupported operations
karmada-detector: Fixed the issue that detector would crash on duplicate registration
Various components: Improved error handling to prevent application crashes and provide better debugging information

[karmada-bot]

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[gemini-code-assist]

Summary of Changes

Hello @PulkitDadwal, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the system's reliability and robustness by replacing panic() calls with structured error handling across various production components. This change prevents application crashes due to errors in areas like the webhook, controller-manager, status controllers, and search proxy, ensuring graceful error management, improved logging, and better debugging capabilities.

Highlights

• Improved Kubernetes Configuration Error Handling: Replaced panic() with klog.Errorf and return fmt.Errorf for Kubernetes configuration retrieval errors in controller-manager, webhook, and customresourceinterpreter components.
• Enhanced Detector Registration Robustness: Implemented graceful error handling for duplicate detector registrations in service-name-resolution-detector-example by logging and returning instead of panicking.
• Refined karmadactl get Watch Error Handling: Enhanced error management in karmadactl get command's watch functionality, replacing panic() with logging and early returns for issues like object retrieval, resource versioning, and watch initiation.
• Graceful Handling of Unsupported Search Proxy Operations: Updated simpleRESTCreateStrategy methods in search proxy to return specific errors or default values instead of panicking for unsupported operations.
• Robustness in Status Controller Condition Handling: Improved error handling in status controllers (federatedresourcequota, workstatus) for unexpected condition statuses, logging the error and returning an fmt.Errorf.
• Better Error Management in Development Tools: Modified utility functions in hack/tools/preferredimports to log errors to os.Stderr and continue processing instead of panicking during file operations.
• Enhanced OrDie Function Diagnostics: Added a log message before panicking in gclient.NewForConfigOrDie and included a note advising against its use in new code, providing more context for unrecoverable errors.

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[gemini-code-assist]

Code Review

This pull request effectively replaces panic() calls with more robust error handling mechanisms across various components, which significantly improves the system's reliability. The changes primarily involve replacing panics with proper error logging and returning errors, or in the case of goroutines, logging the error and exiting the goroutine gracefully.

My review includes a couple of suggestions. One is a high-severity issue where a panic was replaced with a return from a closure, which would silently ignore a critical error. I've recommended using klog.Fatalf to maintain the intended fatal behavior. Another suggestion is a medium-severity improvement to an ...OrDie function to wrap the error in the panic message, preserving the original error context for better debugging.

[gemini-code-assist]

The return statement here only exits the anonymous register function, not NewDetectorInitializers. This means a duplicate detector registration would be silently ignored (apart from the log message), which is likely not the intended behavior. The original panic indicated a fatal error. To maintain this behavior while improving logging, consider using klog.Fatalf which logs the error and exits the program.

Suggested change

	klog.Errorf("Detector name %q was registered twice", name)
	// Return error instead of panic for better error handling
	return
	klog.Fatalf("Detector name %q was registered twice", name)

[gemini-code-assist]

Using fmt.Sprintf here converts the error to a string, which can cause the loss of the original error's type and stack trace. It's better to use fmt.Errorf with the %w verb to wrap the original error. This preserves the error context, which is valuable for debugging when a panic is recovered.

Suggested change

	panic(fmt.Sprintf("failed to create client: %v", err))
	panic(fmt.Errorf("failed to create client: %w", err))