Put an upper bound on "**/Podfile" search depth

[ephemer]

Summary:

This PR addresses https://github.com/react-native-community/cli/issues/2479. Basically the unbounded search for **/Podfile never finishes on my machine. Normally the required depth should be 2, since ios/Podfile is the default location. So this still provides significantly more depth than most users should need.

Test Plan:

To be honest I'm not sure what causes this issue on my system, I only investigated what fixes it so far. It's clearly an issue with a deeply-nested submodule that we have, but I can't see what about it is causing the issue. If I run find . in my project root, all files (including the deeply-nested ones) can be printed within a few seconds, whereas fast-glob appears to never finish its search without this deep: 10 limitation.

Checklist

• [x] Documentation is up to date to reflect these changes.
• [ ] Follows commit message convention described in CONTRIBUTING.md

[thymikee]

Thanks! Can you file that in fast-glob project as well so they can hopefully fix this?