chore(ci): update ui-tests to use start-server-and-test · janus-idp/backstage-plugins@4053345

@janus-idp/backstage-plugin-bulk-import#ui-test: command (/home/runner/work/backstage-plugins/backstage-plugins/plugins/bulk-import) /tmp/yarn--1728671948779-0.189564497894676/yarn run ui-test exited (1)

Process completed with exit code 1.

No files were found with the provided path: plugins/*/playwright-report/. No artifacts will be uploaded.