E2E tests: Add test level into E2E test metadata

What does this MR do and why?

Adds level metadata to E2E tests, so when a failure issue is created the test.level is defined. Level is used in https://gitlab.com/gitlab-org/ruby/gems/gitlab_quality-test_tooling/-/blob/main/lib/gitlab_quality/test_tooling/report/report_as_issue.rb#L63

Example of failure issue with missing level: https://gitlab.com/gitlab-org/gitlab/-/issues/470931

From what I can tell, only E2E tests use this formatter.

Before	After (View rspec json artifact with level added from this MR)
Missing level: https://ops.gitlab.net/gitlab-org/quality/staging/-/jobs/14555050/artifacts/file/gitlab-qa-run-2024-07-05-07-03-35-5f609282/gitlab-ee-qa-576eb428/rspec-14555050.json	GDK https://gitlab-org.gitlab.io/-/gitlab/-/jobs/7282172643/artifacts/qa/tmp/rspec-7282172643-false.json
	CNG https://gitlab-org.gitlab.io/-/gitlab/-/jobs/7282175028/artifacts/qa/tmp/rspec-7282175028-false.json
	package and test https://gitlab.com/gitlab-org/gitlab/-/jobs/7282175090/artifacts/external_file/gitlab-qa-run-2024-07-08-01-18-09-41ff913c/gitlab-ee-qa-7f756ac3/rspec-7282175090.json
	retry https://gitlab.com/gitlab-org/gitlab/-/jobs/7282175106/artifacts/external_file/gitlab-qa-run-2024-07-08-01-18-09-434ecfe3/gitlab-ee-qa-cea50d84-retry/rspec-7282175106.json

Related to #471178