void setValue(long key) {
			cacheMap.put(key, true);
		}
Replace or put datatype pair equivalence state into cache without impacting
its internal activity counter.

@param key datatype identity pair (see
           {@link DataTypeManagerDB#getEquivalenceKey(DataTypeDB, DataType)}
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/DataTypeManagerDB.java