feat: configurable fork

Author: OlivierBBB

testing/src/main/java/net/consensys/linea/testing/MultiBlockExecutionEnvironment.java

@@ -16,7 +16,9 @@
 package net.consensys.linea.testing;
 
 import static net.consensys.linea.reporting.TracerTestBase.chainConfig;
+import static net.consensys.linea.reporting.TracerTestBase.fork;
 import static net.consensys.linea.testing.ToyExecutionEnvironmentV2.DEFAULT_BLOCK_NUMBER;
+import static net.consensys.linea.zktracer.ChainConfig.MAINNET_TESTCONFIG;
 import static net.consensys.linea.zktracer.Trace.LINEA_BLOCK_GAS_LIMIT;
 
 import java.math.BigInteger;