fix(lambda-events): derive Default on KinesisEvent

[sdstolworthy]

📬 Issue #, if available:

✍️ Description of changes:

Adds a default implementation for KinesisEvent.

When using cargo lambda init, the following test is automatically generated:

#[cfg(test)]
mod tests {
    use super::*;
    use lambda_runtime::{Context, LambdaEvent};

    #[tokio::test]
    async fn test_event_handler() {
        let event = LambdaEvent::new(KinesisEvent::default(), Context::default());
        let response = function_handler(event).await.unwrap();
        assert_eq!((), response);
    }
}

This test fails because Default is not implemented on KinesisEvent.

This change provides a basic implementation of default by adding Default to the existing #[derive(...)] attribute.

🔏 By submitting this pull request

• I confirm that I've ran cargo +nightly fmt.
• I confirm that I've ran cargo clippy --fix.
• I confirm that I've made a best effort attempt to update all relevant documentation.
• I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jlizen]

Thanks for fixing this up!

I also cut an issue to double check the remaining events, I'll try to get to it when I have cycles if nobody else does first. #1009