core/vm: add switches to select evm+ewasm interpreters (#17687)

Interpreter initialization is left to the PRs implementing them.
Options for external interpreters are passed after a colon in the
`--vm.ewasm` and `--vm.evm` switches.

cmd/geth/main.go

@@ -130,6 +130,8 @@ var (
 		utils.NoCompactionFlag,
 		utils.GpoBlocksFlag,
 		utils.GpoPercentileFlag,
+		utils.EWASMInterpreterFlag,
+		utils.EVMInterpreterFlag,
 		configFileFlag,
 	}