Move CaptureUnhandledExceptions into config builder

[DJGosnell]

Summary

• Closes Move CaptureUnhandledExceptions into config builder #10

Reason for Change

CaptureUnhandledExceptions was a standalone static method on LogManager with a lifetime decoupled from the logging configuration. Developers had to manually call StopCapturingUnhandledExceptions(), and forgetting to do so leaked event subscriptions. Moving it into the config builder ties its lifecycle to Reconfigure() and Shutdown().

Impact

• LogConfigBuilder gains CaptureUnhandledExceptions(bool observeTaskExceptions = false) method
• LogConfig stores capture flags; handlers are automatically subscribed/unsubscribed during config swaps
• Event handlers now read from _config?.ErrorHandler (the InternalErrorHandler) instead of a separate static delegate
• SetMinimumLevel/SetCategoryOverrides internal methods carry exception capture flags to new configs

Migration Steps

Replace:

LogManager.CaptureUnhandledExceptions(ex => Log.Error(ex), observeTaskExceptions: true);
// ... later ...
LogManager.StopCapturingUnhandledExceptions();

With:

LogManager.Initialize(cfg =>
{
    cfg.InternalErrorHandler = ex => Console.Error.WriteLine(ex);
    cfg.CaptureUnhandledExceptions(observeTaskExceptions: true);
    // ...
});
// Automatically unsubscribed on Reconfigure() or Shutdown()

Performance Considerations

No performance impact — same Interlocked guard pattern, same event handler logic.

Security Considerations

None.

Breaking Changes

• Consumer-facing: LogManager.CaptureUnhandledExceptions() and LogManager.StopCapturingUnhandledExceptions() public methods removed. Exception handler parameter removed — routes to InternalErrorHandler instead.
• Internal: _exceptionHandler static field removed from LogManager.