zkevm-demo: save transaction locally instead of using rpc node

[Erik Kaneda]

Bug Report

Currently, the zkevm demo calls out to an rpc node during testing. This is eating up our usage of free API's. There are security implications to using an API key so let's just save the tx data within the examples repo instead of calling out to eth rpcs.

Steps to Reproduce

1. cd examples
2. cargo test
3. cargo test will call out to an ETH RPC.

Expected behavior

Change step 3 to use saved data rather than downloading from eth rpc.

Your Environment

• risc0-zkvm version: 0.21
• Rust version: 1.74
• Platform/OS: macOS

Additional context

If this is not fixed, it could block ci from running

[linear]

ZKVM-387 [BUG] zkevm-demo: save transaction locally instead of using rpc node

[Erik Kaneda]

The code is here:

risc0/examples/zkevm-demo/core/src/lib.rs

Line 271 in 93c1a11

 async fn trace_tx() {