fix: switch to relay webhooks

[chris13524]

Description

Switches from websocket client to webhooks 2.0 according to the proposed approach outlined here.

Resolves #235

Depends on #343

Remaining work:

• relay_public_key variable added to TF cloud
• Verify aud
• Verify iss
• batchReceive messages. Blocked by https://walletconnect.slack.com/archives/C05ABTQSPFY/p1706640165101309
• Re-enable unsubscribe in notifyDelete: https://walletconnect.slack.com/archives/C05ABTQSPFY/p1706307603828609
• Re-implement deployment tests
• New unit tests
  • Registers with 30 day expiration
  • Wrong iss is rejected in webhook handler
  • batchReceive is called (i.e. fetch fails)
• Update implementation to match specs: https://walletconnect.slack.com/archives/C05ABTQSPFY/p1706305922028699
• Restore 4050 publishing for topics on resubscribe
• Batch receive service
• Merge https://github.com/WalletConnect/rs-relay/pull/1427 and use tagged version

For subsequent PRs:

• Subscription to topic is not guaranteed #303
• Renew topic subscriptions only when they need to be #325
• Define procedure for rotating keypair seed and resolve issues #354

How Has This Been Tested?

Existing and new tests

Due Diligence

• Breaking change
• Requires a documentation update
• Requires a e2e/integration test update

[geekbrother]

LGTM!