refactor: remove `ViewModels.WorkingCopy.StashAllAsync` method #3775

Job	Run time
Prepare version string	4s
Build / Build Windows ARM64	3m 38s
Build / Build macOS (Intel)	5m 19s
Build / Build Windows x64	3m 48s
Build / Build macOS (Apple Silicon)	3m 18s
Build / Build Linux (arm64)	3m 30s
Build / Build Linux	3m 20s
Package / Package Windows (win-arm64)	21s
Package / Package macOS (osx-x64)	23s
Package / Package macOS (osx-arm64)	18s
Package / Package Windows (win-x64)	29s
Package / Package Linux (linux-arm64)	49s
Package / Package Linux (linux-x64)	53s
	26m 10s

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