Fixes #31504

This is done mostly so that we can refer to MIR types in csearch and other metadata related area.

lvalues and operands

module and into `hair/cx`, now that we don't have a trait defining
the interface

This commit contains some of the changes proposed by a rustfmt invocation,
chosen based on the fairly non-deterministic metric of how much I liked the
change. I expect we will run rustfmt on this crate again later, probably
accepting more of its changes. For now, this is already an improvement over
the status-quo.

trees in MIR