Updates package manager detection to account for two lock files. All other managers will only have the one lock file. Bun, however, may have both a `bun.lockb` _and_ a `yarn.lock` file. To ensure bun is properly detected, the presence of `bun.lockb` with `yarn.lock` must occur before `yarn.lock` so we don't mistake the presence of a `yarn.lock` to mean "Yarn".
This PR also adds a test for this situation in `fs-detectors`. The behavior is currently correct there, but was not tested initially. It is now to avoid future regressions.
The code for these two are almost identical, so consolidate into one codebase.
Also adjusts the `pnpm test` script to allow for specifying a file name to be executed, instead of running all tests.
### Related Issues
Improves how `vc build` handles monorepos. In short, this introduces
monorepo manager detection logic and then some helpful defaults so users
don't have to manually specify a `buildCommand` or `installCommand` when
linking a project within a monorepo.
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Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>
