Remove `Rust::make_unique` #8316

Job	Run time
build-and-check-clang-macos	19m 27s
build-and-check-gcc-5	10m 36s
build-and-check-ubuntu-32bit	24m 46s
build-and-check-ubuntu-64bit	25m 43s
build-and-check-ubuntu-64bit-glibcxx	25m 47s
build-and-check-asan	29m 43s
	2h 16m 2s

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