refactor(useFilenamingConvention): accept filename in unicase

[Conaclos]

Summary

Fix #3353

By fixing this issue, we also now accept filenames in unicase.
This aligns the behavior of useFilenamingConvention with the behavior of useNamingConvention.

Test Plan

I added two tests.

[codspeed-hq]

CodSpeed Performance Report

Merging #3356 will improve performances by 6.15%

_{Comparing conaclos/unicase-filename (15f0f3c) with main (7e485c2)}

Summary

⚡ 1 improvements
✅ 107 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	conaclos/unicase-filename	Change
⚡	router_14177007973872119684.ts[cached]	2.2 ms	2.1 ms	+6.15%