Change to async/await for update member role

What does this MR do and why?

Related to #391943

Update the updateMemberRole call in role_dropdown to async/await pattern with a try/catch. Additionally adds test coverage for Sentry logging.

Screenshots or screen recordings

Before	After
stuck_update	fixed_update

Error message thrown from actions.js

How to set up and validate locally

• Smoke test baseline max role update behavior
  • Open up the rails console rails c and enable the show_overage_on_role_promotion flag (Feature.enable(:show_overage_on_role_promotion))
  • Navigate to the project members page for a project (ex: gitlab-org/gitlab-shell/-/project_members)
  • Change the Max role from Guest to a higher value (Maintainer/Owner) and click Continue
  • This should be successful

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.