Fix Amazon Q not triggering with new issuable

• Feature branch: DRAFT: Amazon q spike (!174614 - closed)
• Side note: This was originally developed in a private fork by GitLab team members in collaboration with Amazon's team.

What does this MR do and why?

!176221 (merged) did not quite work when issuing a /q quick action from a new issue or merge request. The amazon_q_params is a type ActionController::Parameters since it is passed from the controller. Add a test and relax the type check.

References

• https://docs.gitlab.com/ee/user/duo_amazon_q/

How to set up and validate locally

1. Set up Amazon Q (I used a package from https://gitlab.com/gitlab-org/omnibus-gitlab/-/jobs/8699840093). See https://gitlab.com/gitlab-com/ops-sub-department/aws-gitlab-ai-integration/integration-motion-planning/-/wikis/integration-docs.
2. Create a new issue with /q dev in the description.