Auto merge of #97740 - RalfJung:ctfe-cycle-spans, r=lcnr

use precise spans for recursive const evaluation

This fixes rust-lang/rust#73283 by using a `TyCtxtAt` with a more precise span when the interpreter recursively calls itself. Hopefully such calls are sufficiently rare that this does not cost us too much performance.

(In theory, cycles can also arise through layout computation, as layout can depend on consts -- but layout computation happens all the time so we'd have to do something to not make this terrible for performance.)

Author: bors