Specifically, we previously emitted a "compiler doesn't understand error", so we
were always emitting an error appropriately. This just gives a better error
message saying instead that the compiler did understand what happened and that
one cannot apply consume to globals or escaping captures.
https://github.com/apple/swift/issues/67755
rdar://112561671
I discovered when working with improving the debug output of the move only
address checker that I had a need for lightweight thing like
DebugVarCarryingInst but that only could vend a VarDecl (unlike
DebugVarCarryingInst which also can vend a SILDebugVariable). As an example,
this lets one write a high level API that uses the standard API to loop over a
bunch of instructions all that vend a VarDecl and construct a stringified path
component list.
rdar://105293841
