Rename ChannelReference to ChannelInterface in the IR. A ChannelInterface (formerly ChannelReference) is a construct in the proc-scoped channel world which binds to a channel. A ChannelInterface is referred to by send and receive nodes and contains the necessary metadata for interfacing with a channel. An alternative name considered is channel endpoint or channel end, but I think interface better captures the concept as multiple channel interfaces may be stacked on top of each other (nested) via proc instantiation. An end point implies the single termination point of a channel. PiperOrigin-RevId: 734000400