Combine Coreplex and System Module Hierarchies (#875)

* coreplex collapse: peripherals now in coreplex

* coreplex: better factoring of TLBusWrapper attachement points

* diplomacy: allow monitorless :*= and :=*

* rocket: don't connect monitors to tile tim slave ports

* rename chip package to system

* coreplex: only sbus has a splitter

* TLFragmenter: Continuing my spot battles on requires without explanatory strings

* pbus: toFixedWidthSingleBeatSlave

* tilelink: more verbose requires

* use the new system package for regression

* sbus: add more explicit FIFO attachment points

* delete leftover top-level utils

* cleanup ResetVector and RTC