Parallel encryption across multiple regions

[DarrellMozingo]

When multiple encryption providers are defined, can the DefaultCryptoMaterialsManager encrypt the additional providers in parallel rather than serially? Biggest use case for this would be having KMS providers defined in multiple disparate regions (Asia/Europe/US) and reducing the time waiting for each to contact them.

Thanks!

[mattsb42-aws]

This is definitely something that I could see being useful; we've had some other feedback that encrypting with many KMS master keys can inconveniently long, so I think it would be worth pursuing.

We are currently in the process of figuring out an RFC process, and this would be a great candidate for testing that out once we have a working starting point for the process.

I'll update this issue once we have that process sorted out.