Fix MR widget tests

What does this MR do and why?

Fix MR widget tests

• another MR for this file, it is large and unruly, but getting closer to being Vue3 compliant
• remove some vm checks and vm assigns
• organize the file to make it more customizable

What does this MR not do and why?

• fixes every issue in this file because there are a lot of them
• see https://gitlab-org.gitlab.io/frontend/playground/vue-compat-scanner/ for what is left

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.

Related to #391157 (closed)