Rollup merge of #147189 - yotamofek:pr/rustdoc/highlight-optimizations-2, r=GuillaumeGomez

Replace `rustc_span::Span` with a stripped down version for librustdoc's highlighter

While profiling rustdoc's syntax highlighter, I noticed a lot of time being spent in the `Span` interner, due to the highlighter creating a lot of (new) spans.
Since the only data from the `Span` that we use is the `hi` and `lo` byte positions - I replaced the regular `Span` with a simple one with two fields, and in my benchmarks it seemed to make a big dent in the highlighter's perf, so thought I would see what the perf runner says.

0 files changed, 0 insertions, 0 deletions