[12.x] Add --json option to EventListCommand

[hotsaucejake]

Summary
This pull request adds an optional --json flag to the event:list command so that it can return events and listeners in JSON format, similar to other Laravel commands like route:list, about, model:show, and db:table.

• Brings event:list into parity with other Artisan commands that provide both traditional CLI output and a JSON option.
• Introduces a --json flag to output the event/listener data as JSON.
• Preserves all existing CLI output and behavior.
• Non-breaking change: all existing tests pass unchanged, while new tests ensure the JSON output works correctly.

Future
There are other commands that could similarly use an optional --json flag, such as ListFailedCommand, ConfigShowCommand, ChannelListCommand, and ScheduleListCommand. I can make separate pull requests for these.

Testing

• Existing tests for event:list remain unmodified and still pass.
• Added new coverage to verify JSON output, including cases for an empty list, a populated list, and usage with filters.