Add support for file path patterns

[carlosflorencio]

When running against a file require("neotest").run.run(path), the file type is file and we should filter the test runner to target only that file (else the pattern will be --testNamePattern='.*' == all tests).

This change makes the test runner pattern --testPathPattern='filename.ts' when the type is file.

[haydenmeade]

LGTM probably just need to fix up UT