boolean activateResolveCache() {
		if (resolveCache != null) {
			return false;
		}
		resolveCache = new IdentityHashMap<>();
		return true;
	}
Activate resolveCache and associated resolveQueue if not already active. If
this method returns true caller is responsible for flushing resolveQueue and
invoking {@link #processResolveQueue(boolean)} when resolve complete. 
For each completed resolve {@link #cacheResolvedDataType(DataType, DataType)} 
should be invoked.

@return true if resolveCache activated else false if already active.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/DataTypeManagerDB.java