The LoadableDescriptors attribute supports all FieldDescriptors which are expressed with the following grammar:
```
FieldDescriptor:
  FieldType

FieldType:
  BaseType
  ClassType
  ArrayType

BaseType:
  (one of)
  B C D F I J S Z

ClassType:
  L ClassName ;

ArrayType:
  [ ComponentType

ComponentType:
  FieldType
```

Only the "ClassType" descriptors are meaningful to the JVM as they are ones which can be speculatively loaded.

Update the classFileParser logic to:
1) Validate all LD elements as FieldDescriptors (already what it does today)
2) Drop the non-ClassType (ie: non "L" Foo ";") elements so the rest of the JVM never sees them,