[pmlib] specialize hash for mem_msgs for verilog gen caching
[pmlib] specialize hash for mem_msgs for verilog gen caching

tj93/pymtl,cfelton/pymtl,jjffryan/pymtl,tj93/pymtl,jjffryan/pymtl,Glyfina-Fernando/pymtl,tj93/pymtl,jck/pymtl,cfelton/pymtl,12yujim/pymtl,Glyfina-Fernando/pymtl,jjffryan/pymtl,jck/pymtl,cornell-brg/pymtl,jck/pymtl,12yujim/pymtl,12yujim/pymtl,cornell-brg/pymtl,Glyfina-Fernando/pymtl,cfelton/pymtl,cornell-brg/pymtl