vm: add Synthetic modules

- Refactor vm.SourceTextModule (again)
- Add vm.Module abstract superclass
- Add vm.SyntheticModule

Refs: https://heycam.github.io/webidl/#synthetic-module-records

PR-URL: #29864
Reviewed-By: Guy Bedford <[email protected]>

Author: devsnek

doc/api/errors.md

@@ -1984,7 +1984,7 @@ The linker function returned a module for which linking has failed.
 <a id="ERR_VM_MODULE_NOT_MODULE"></a>
 ### ERR_VM_MODULE_NOT_MODULE
 
-The fulfilled value of a linking promise is not a `vm.SourceTextModule` object.
+The fulfilled value of a linking promise is not a `vm.Module` object.
 
 <a id="ERR_VM_MODULE_STATUS"></a>
 ### ERR_VM_MODULE_STATUS