Offline caching improvements - Delay between and backoff when 429 is on

[bruno-garcia]

The SDK guideline has a couple of new items regarding offline caching: getsentry/develop#509

Retry on the background is tracked here: #803 but two main items are new:

1. If rate-limit was hit, make sure the caching transport is aware. Meaning: don't read all files from disk to send to the HTTP transport when that's basically dropping everything due to rate-limit
2. Add a delay when reading from disk to avoid bursts of events which could trigger rate limit

• Offline caching improvements - Delay between and backoff when 429 is on sentry-cocoa#1671
• Offline caching improvements - Delay between and backoff when 429 is on sentry-java#1926

[bruno-garcia]

https://develop.sentry.dev/sdk/features/#additional-capabilities