Cleanup coalesce transform tests

[rukai]

prereq for https://github.com/shotover/shotover-proxy/pull/1717

1717 requires changes to these tests that will become a lot easier if avoid the duplication in the tests

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #1718 will not alter performance

_{Comparing rukai:cleanup_coalesce_tests (833318e) with main (9bb7faa)}

Summary

✅ 39 untouched benchmarks