refactor: add support for running specific test files

[yvonneyx]

Run specific test files

You can specify which test files to run using the --file or -f option:

# Run a single test file
npx perf --file test.perf.ts

# Run multiple test files
npx perf --file test1.perf.ts test2.perf.ts

# Short form
npx perf -f test.perf.ts

By default, iPerf will run all files matching the pattern **/*.perf.ts in your project.