message: [language] Make execution stack visible for runtime tests
  tests in the vm_runtime directory were broken since the execution_stack
  was not available when testing. This updates the config variable around
  this field to make this field visible for both instruction synthesis,
  and testing.
  Closes:
  Approved by: tzakian
diff: @@ -88,10 +88,10 @@ where
  'alloc: 'txn,
  P: ModuleCache<'alloc>,
  {
  - #[cfg(feature = "instruction_synthesis")]
  + #[cfg(any(test, feature = "instruction_synthesis"))]
  pub execution_stack: ExecutionStack<'alloc, 'txn, P>,
  - #[cfg(not(feature = "instruction_synthesis"))]
  + #[cfg(not(any(test, feature = "instruction_synthesis")))]
  execution_stack: ExecutionStack<'alloc, 'txn, P>,
  gas_meter: GasMeter,
  txn_data: TransactionMetadata,
  