Auto merge of #36025 - michaelwoerister:incr-comp-hash-spans, r=nikomatsakis

Auto merge of #36025 - michaelwoerister:incr-comp-hash-spans, r=nikomatsakis

incr. comp.: Take spans into account for ICH

This PR makes the ICH (incr. comp. hash) take spans into account when debuginfo is enabled.

A side-effect of this is that the SVH (which is based on the ICHs of all items in the crate) becomes sensitive to the tiniest change in a code base if debuginfo is enabled. Since we are not trying to model ABI compatibility via the SVH anymore (this is done via the crate disambiguator now), this should be not be a problem.

Fixes #33888.
Fixes #32753.