Add multi-URL client connect method.

[its-saeed]

Summary

Add multi-URL client connect method.

Breaking Changes

Checklist

• All changes are covered by tests (or not applicable)
• All changes are documented (or not applicable)
• I reviewed the entire PR myself (preferably, on GH UI)
• I described all Breaking Changes (or there's none)

[cursor]

PR Summary

Adds fallback-enabled multi-URL connection for Provider/RetryableClient and pins fuel-core* deps to a specific git revision.

• fuels-accounts:
  • Connection:
    • Add Provider::connect_with_fallbacks(urls) and make Provider::connect delegate to it.
    • Add RetryableClient::connect_with_fallbacks(urls, retry_config) using FuelClient::with_urls.
    • Remove stored url in RetryableClient; url() now returns client.get_default_url().
  • Types:
    • Derive Clone for custom_queries::IsUserAccountVariables.
• Dependencies:
  • Pin fuel-core, fuel-core-chain-config, fuel-core-client, fuel-core-poa, fuel-core-services, fuel-core-types to a specific git rev.

^{Written by Cursor Bugbot for commit b42bcda. This will update automatically on new commits. Configure here.}