ci: Add temporary database setup for performance tests

[ogabrielluiz]

This pull request introduces a temporary database setup for performance tests by creating a fixture that sets a test database URL. The fixture ensures that the original database URL is restored after the tests are completed. Additionally, assertions have been added to various performance tests to verify that the temporary database URL is being used during the tests. This change enhances the reliability of performance testing by isolating the test environment.

[codspeed-hq]

CodSpeed Performance Report

Merging #4469 will degrade performances by 28.27%

_{Comparing improve-benchmarks (7842a2f) with main (ed69253)}

Summary

⚡ 1 improvements
❌ 2 regressions
✅ 12 untouched benchmarks

⁉️ 1 dropped benchmarks

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

Benchmarks breakdown

	Benchmark	main	improve-benchmarks	Change
❌	test_load_flows	945.5 µs	1,318.1 µs	-28.27%
❌	test_setup_llm_caching	1.1 ms	1.6 ms	-27.36%
⚡	test_successful_run_with_input_type_any	528.3 ms	471.5 ms	+12.06%
⁉️	test_successful_run_with_input_type_chat	451.4 ms	N/A	N/A