Gracefully handle exceptions

Rails does has builtin rescue mechanism at middleware level called ActionDispatch::ShowExceptions. This wasn't functioning properly since we introduced Gitlab::Middleware::HandleMalformedStrings as it was raising exception before ActionDispatch::ShowExceptions. Fix here is to move the ActionDispatch::ShowExceptions up in the middleware stack.

This seems to be a regression from !112909 (merged)

Context: gitlab-com/gl-infra/production#16421 (comment 1595995965)

How to set up and validate locally

Run the following command, and ensure that it returns 400, not 500 error

 curl -v --request POST https://gdk.test:3000 --data '{"in{valid_js{on"}' --header "Content-Type: application/json"

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.