This makes it possible to treat chained composition associatively.
x := y :=? z :=* a ...
It also makes it easy to chain multiple optional adapters:
node :=? (Seq(a, b) ++ c ++ d)
* 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