Auto merge of #115657 - Zoxc:source-span-avoid-query, r=cjgillot

Avoid a `source_span` query when encoding Spans into query results

This avoids a `source_span` query when encoding `Span`s into query results. It's not sound to execute queries here as the query caches can be locked and the dep graph is no longer writable.

r? `@cjgillot`