test: add CLI flag to disable test, spec filename filter

[DonIsaac]

What is the problem this feature would solve?

Many repos using tap or mocha put test files in a test folder without test or spec in their names. Migrating to bun test requires renaming all of their test files.

What is the feature you are proposing to solve the problem?

Add a CLI flag (maybe something like bun test --all-files) or an environment variable to disable filename filtering.

What alternatives have you considered?

Renaming all test files. While doable, it adds an extra step for migrating older repos to bun.

[Electroid]

We could also do something like bun test --style=mocha, which would allow us to do a bunch of other stuff, specific to mocha. Even better if we can just figure this out automatically from your package.json.