resolve: Improve performance

[jseyfried]

This fixes #33061 by speeding up searchs through all traits in scope, a bottleneck in resolve.

According to my measurements, this PR improves resolution performance by a factor of 3.4x on librustc, which almost completely reverses the 3.75x performance regression reported in #33061.

r? @eddyb

[jseyfried]

cc @nikomatsakis

[eddyb]

@bors r+

[bors]

📌 Commit 6ae8027 has been approved by eddyb

[bors]

⌛️ Testing commit 6ae8027 with merge 63760ac...

[jseyfried]

@eddyb thanks! The regression is currently in beta -- do you think we should beta-nominate this?

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-mir, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-64-x-armhf, auto-linux-64-x-armsf, auto-linux-64-x-freebsd, auto-linux-64-x-netbsd, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-cross-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-mir, auto-win-msvc-64-opt-rustbuild

[nikomatsakis]

Ordinarily we wouldn't backport a pure performance change, but approved for beta because:

• this is a small and simple patch;
• it's a perf regression, no need to give up ground.