[DAR-5422][External] API-wide HTTP 429 and 5xx handling

[JBWilkie]

Problem

Darwin recently introduced some API-wide rate limits. If they are exceeded, they will return an HTTP 429 error. Historically, darwin-py has not had handling for 429 errors, except for 1 specific functionality: Registering items from external storage

Solution

Resolve this by:

• 1: Applying the existing backoff and retry code (implemented with tenacity) to the generic get, post, put, and delete Client class methods
• 2: Funnel as many Darwin API calls through these methods as is practical and reasonable

We also include the 500, 502, 503 and 504 as codes that trigger retries - These were previously used to retry some requests in darwin-py as protection against temporary drops in external API services

There are some exceptions that are acceptable - Such as in client.from_api_key() when creating a Client object. This is because the back & retry code is applied to Client methods

Changelog

Introduced API-wide rate limit and server error retry handling intro darwin-py

[linear]

DAR-5422 Add `429` handling to all requests sent by darwin-py