Make `test-package-with-data` a flat-layout package to restore skipped failing test #266

Performance Regression: -30.39%

❌ 1 regressed benchmark
✅ 4 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

	Benchmark	`BASE`	`HEAD`	Efficiency
❌	`test_build_conda[imagesize]`	51.1 ms	73.4 ms	-30.39%

_{Comparing agriyakhetarpal:undo-test_install_installer_data_files_present-skip (4144ef3) with main (836a0f3)¹}

No successful run was found on main (3689748) during the generation of this report, so 836a0f3 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩