Use detailed_merge_status in E2E tests instead of merge_status

What does this MR do and why?

• Stops using the deprecated merge_status attribute and use detailed_merge_status instead for a more reliable, synchronous status check.
• Logs when the test attempts to merge via the API.
• On timeout, include the final merge status in the error raised.

Fixes #412335 (closed), #412392 (closed), #412389 (closed), #412372 (closed)

How to set up and validate locally

cd qa
bundle exec rspec qa/specs/features/ee/browser_ui/10_govern/group/group_compliance_dashboard_spec.rb \
  qa/specs/features/api/3_create/merge_request/push_options_target_branch_spec.rb \
  qa/specs/features/api/3_create/merge_request/push_options_title_description_spec.rb

MR acceptance checklist

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