App hosting should support pnpm workspace projects

### [REQUIRED] Environment info

**firebase-tools:** 13.13.0

**Platform:** MacOS

### [REQUIRED] Test case

Steps to reproduce should be enough

### [REQUIRED] Steps to reproduce

1. Create a new pnpm workspace with the following pnpm-workspace.yaml
```yaml
packages:
- "apps/*"
- "packages/*"
```
2. inside `/apps/main` init a new nextjs app
3. inside `/packages/random` init empty js project
4. in project root run `pnpm i`
5. commit and push to Github
6. create new app hosting backend, specify app directory to `/apps/main`

### [REQUIRED] Expected behaviour

Deploys the app

### [REQUIRED] Actual behaviour

failed to build, lockfile not found