Auto merge of #160539 - obi1kenobi:pg/normalizes-to-reuse-ref, r=lcnr

[perf] Reuse existing trait reference instead of recreating it.

Effectively, do one step of common subexpression elimination, manually. We can reuse the existing interned reference made a few lines prior, without needing to recreate it.

r? @lcnr

**AI disclosure:** The optimization opportunity here was discovered as part of a systematic probe for missed optimizations using a combination of both traditional and AI tools. The code here was initially prototyped and vetted by AI tools, followed by additional manual work. I stand behind the quality of the code I'm submitting, and I vouch it's as good or better than if no AI tools were in the loop.

Author: bors