void clear() {
		dataTypeCache = new HashMap<>();
	}
Ensures that the data type managers are used in a particular order.
The order is as follows:
   1) the program's data type manager
   2) the built-in data type manager
   3) the open data type archives
Ghidra/Features/PDB/src/main/java/ghidra/app/util/bin/format/pdb/PdbDataTypeParser.java