sylab/multi-clock: HPCA 2022 paper codebase and artifacts

This is the version of Multi-Clock that was used for experiments reported in the following HPCA paper: MULTI-CLOCK: Dynamic Tiering for Hybrid Memory Systems, A. Maruf, A. Ghosh, J. Bhimani, D. Campello, A. Rudoff, and R. Rangaswami, Proceedings of the 28th IEEE International Symposium on High-Performance Computer Architecture (HPCA-28), Seoul, South Korea, 2022