cmd/evm: add state transition tool for testing (#20958)

This PR implements the EVM state transition tool, which is intended
to be the replacement for our retesteth client implementation.
Documentation is present in the cmd/evm/README.md file.

Co-authored-by: Felix Lange <fjl@twurst.com>

tests/init.go

@@ -19,6 +19,7 @@ package tests
 import (
 	"fmt"
 	"math/big"
+	"sort"
 
 	"github.com/ethereum/go-ethereum/params"
 )
@@ -154,6 +155,16 @@ var Forks = map[string]*params.ChainConfig{
 	},
 }
 
+// Returns the set of defined fork names
+func AvailableForks() []string {
+	var availableForks []string
+	for k := range Forks {
+		availableForks = append(availableForks, k)
+	}
+	sort.Strings(availableForks)
+	return availableForks
+}
+
 // UnsupportedForkError is returned when a test requests a fork that isn't implemented.
 type UnsupportedForkError struct {
 	Name string