(Again) Attempt to implement `Locker` for `Isolate` #6211

Job	Run time
debug x86_64-apple-darwin	8m 12s
release x86_64-apple-darwin	8m 19s
asan aarch64-apple-darwin	8m 16s
debug aarch64-apple-darwin	8m 16s
release aarch64-apple-darwin	8m 15s
debug x86_64-unknown-linux-gnu	6m 54s
release x86_64-unknown-linux-gnu	6m 37s
release x86_64-pc-windows-msvc	7m 58s
debug aarch64-unknown-linux-gnu	8m 8s
release aarch64-unknown-linux-gnu	8m 7s
publish	0s
	1h 19m 2s

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