Render event information in aws-ruby handler template

[ktopolski]

What did you implement:

Enhanced aws-ruby handler template to render event information in response JSON, just like aws-nodejs template does.

Closes #6462

How did you implement it:

Changed handler.rb to render event information under input key in body - just like in aws-nodejs template. Also - ditched JSON.generate in favor of to_json, since JSON.generate is invalid syntax till ruby-2.4.0 and it may be discouraging for new people.

How can we verify it:

$ bin/serverless -t aws-ruby --path test
$ cd test
$ serverless deploy # given aws configured
$ curl -X GET url-gained-from-previous-output

Todos:

Note: Run npm run test-ci to run all validation checks on proposed changes

• Write tests and confirm existing functionality is not broken.
  Validate via npm test
• Ensure there are no lint errors.
  Validate via npm run lint-updated
  Note: Some reported issues can be automatically fixed by running npm run lint:fix
• Ensure introduced changes match Prettier formatting.
  Validate via npm run prettier-check-updated
  Note: All reported issues can be automatically fixed by running npm run prettify-updated
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[pmuens]

Thanks @ktopolski 👍

LGTM