Make transactions in execution layer integration tests (#3320)

## Issue Addressed

Resolves #3159 

## Proposed Changes

Sends transactions to the EE before requesting for a payload in the `execution_integration_tests`. Made some changes to the integration tests in order to be able to sign and publish transactions to the EE:

1. `genesis.json` for both geth and nethermind was modified to include pre-funded accounts that we know private keys for 
2. Using the unauthenticated port again in order to make `eth_sendTransaction` and calls from the `personal` namespace to import keys

Also added a `fcu` call with `PayloadAttributes` before calling `getPayload` in order to give EEs sufficient time to pack transactions into the payload.

testing/execution_engine_integration/src/geth.rs

@@ -90,13 +90,14 @@ impl GenericExecutionEngine for GethEngine {
             .arg(datadir.path().to_str().unwrap())
             .arg("--http")
             .arg("--http.api")
-            .arg("engine,eth")
+            .arg("engine,eth,personal")
             .arg("--http.port")
             .arg(http_port.to_string())
             .arg("--authrpc.port")
             .arg(http_auth_port.to_string())
             .arg("--port")
             .arg(network_port.to_string())
+            .arg("--allow-insecure-unlock")
             .arg("--authrpc.jwtsecret")
             .arg(jwt_secret_path.as_path().to_str().unwrap())
             .stdout(build_utils::build_stdio())