RetryConfig and TimeoutConfig in file_store

[kurotych]

When a connection problem occurs, downloading a file from AWS hangs.
Add the ability to configure timeout and retry policies in the file_store.

[michaeldjeffrey]

Can we get these added to Settings as well so calls to FileStore::from_settings can pick them up?

[kurotych]

Can we get these added to Settings as well so calls to FileStore::from_settings can pick them up?

I think we can but should we?
I can't just add TimeoutConfig and RetryConfig structs into Settings because the Settings type is directly mapped to the config file and I'm not sure how much and what exact config parameters from these two aws configs should I include to Settings. Also, after I include them we should start to support these config parameters (with backward compatibilities). I think we shouldn't hurry in this case.