Add a complete set of drcachesim unit tests

Copying from https://github.com/DynamoRIO/dynamorio/issues/4841#issuecomment-814452409

Unfortunately drcachesim does not have good unit tests today: mostly it has end-to-end tests comparing golden output with broad regexes to account for system differences, which are not ideal. Xref #3195, though simple tests could be created just using short local arrays of memref_t.

This issue covers adding such unit tests to provide better confidence and regression testing of simulator features than the end-to-end broad regexes provide.