[x] Create new handshake::BufferOp operation and related handshake::TimingAttr.
[x] Add new RTL parameter type to the backend corresponding to the handshake::TimingAttr (this requires support for complex RTL types, which should be added as part of the type system redesign).
[x] Adapt the existing buffer placement pass to the new buffer operation.
[x] Delete existing handshake::OEHBOp and handshake::TEHBOp buffer operations, and slightly refactor passes that use them.
Tracking issue for buffering redesign, described in this specification.
handshake::BufferOpoperation and relatedhandshake::TimingAttr.handshake::TimingAttr(this requires support for complex RTL types, which should be added as part of the type system redesign).handshake::OEHBOpandhandshake::TEHBOpbuffer operations, and slightly refactor passes that use them.