Enhance retry with Best Practices for Backoff and Jitter

[mawelborn]

Refactors and enhances the @retry() decorator with:

• Best practices for exponential backoff and jitter
  • Configurable retry count, base wait time, backoff multiplier, and jitter multiplier
  • Reasonable defaults that retry 4 times over the course of ~2 minutes
    • With 1, 4, 16, and 64 second waits (+ up to 50% jitter)
• Cleaner function signature for specifying errors to retry on
• More thorough type checks
• Unshadows the retry module