docs: update flagd provider specs

[toddbaert]

This PR contains significant enhancements to flagd provider specs. If merged, I will be opening a bunch of issues to implement what's described here based on recon I've been doing with the existing implementations

Specifically:

• adds retryGraceAttempts param, which defines the amount of stream retry attempts before provider moves from STALE to ERROR state
• adds contextEnricher param, which defines mapping function for sync-metadata to evaluation context for in process providers (exists already in Java provider)
• improves consistency between in-process and RPC stream reconnect behavior
• simplifies provider doc and spec to remove duplication and improve readability

[netlify[bot]]

✅ Deploy Preview for polite-licorice-3db33c ready!

Name	Link
🔨 Latest commit	075efb716abb358136b6d83aaa791517fbdc13e5
🔍 Latest deploy log	https://app.netlify.com/sites/polite-licorice-3db33c/deploys/672275579bdd330008eb1037
😎 Deploy Preview	https://deploy-preview-1432--polite-licorice-3db33c.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[toddbaert]

Build failure is due to Trivvy rate limit.