feat(alloy-provider): implement fetch block

[cakevm]

Add the block(...), block_by_id(...) implementation for the alloy-provider.

Thanks to 🤖 Claude Code for support

[codspeed-hq]

CodSpeed Performance Report

Merging #16934 will not alter performance

_{Comparing cakevm:rpc-to-block (4e83735) with main (faa9d37)}

Summary

✅ 77 untouched benchmarks