[Perf] Widespread regressions after threadpool change #44211
Description
After #43841, we are seeing widespread (about 40 tests) regress. Some of these are threading tests, but some seem to have little to do with threading, like DrewScoggins/performance-2#3177. Below I have a link to a query that is all of the regressions and a few improvements that are linked to this change. We are seeing this across Windows x64, x86 and Ubuntu x64, and I will be updating this issue as we get the Windows x86, and Ubuntu x64 regressions categorized.