Rust optimizer improvements #4187

Job	Run time
Check for upstream trigger phrase	3s
Test importing with bare requirements	12m 42s
Build & Test (ubuntu-latest, python: 3.8, distributed: false)	8m 42s
Build & Test (ubuntu-latest, python: 3.9, distributed: false)	8m 54s
Build & Test (ubuntu-latest, python: 3.10, distributed: false)	8m 52s
Build & Test (windows-latest, python: 3.8, distributed: false)	14m 31s
Build & Test (windows-latest, python: 3.9, distributed: false)	18m 26s
Build & Test (windows-latest, python: 3.10, distributed: false)	17m 39s
Build & Test (macos-latest, python: 3.8, distributed: false)	12m 49s
Build & Test (macos-latest, python: 3.9, distributed: false)	10m 50s
Build & Test (macos-latest, python: 3.10, distributed: false)	22m 21s
Build & Test (ubuntu-latest, python: 3.8, distributed: true)	9m 1s
Build & Test (ubuntu-latest, python: 3.10, distributed: true)	9m 21s
	2h 34m 11s

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