Add configurable "shared with me" output dir

[Bungeefan]

Closes #277

This PR adds the requested "Shared with me" directory setting, along with the following improvements:

• Replaced manual ownedByMe check with a Drive API query parameter
• Move user-owned folders that exist in "shared" folders into the "Shared with me" folder
• Implemented the import of shared files (files without any parent folders)
  • Unfortunately, for this feature, I had to fallback to a local check (empty parents) as I was unable to reach the same result with the Google Drive Query API.

Feel free to request changes, I am myself not super happy with the implementation, but further improvements would require more refactoring, which I didn't feel comfortable starting without any feedback/guidance (therefore, I tried to change as little as possible while still preventing duplicated code).

[lukasdotcom]

Hi @Bungeefan 👋,

Thanks so much for the comprehensive pr. I tested it and it worked on my simple test accounts 🎉. I've added some feedback.

[lukasdotcom]

You have a failing check that can be fixed with composer cs:fix, but other then that it looks good. If there are any specific refactoring you want to do I can tell you if they make sense.

[Bungeefan]

Thanks for the review, fixed the obsolete import.

As I could already remove a lot of the parameters from the retrieveFiles function, I am now fine with that.
However, I am still debating about the optional $allowParents parameter, but besides aesthetics I don't think there is really much to improve in its current state and, at first, I was unsure about the addition of $sharedDirectoriesById and therefore separation from $directoriesById (instead of just a flag in the original array), but I guess it's fine either way.

If you have no further objections, feel free to merge it.

[lukasdotcom]

Thanks. I'll merge it then 🚀

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