feat(fs/unstable): add readDir #16262

Job	Run time
lint (ubuntu-latest)	25s
lint (windows-latest)	43s
test (v1.x, ubuntu-latest)	1m 19s
test (v1.x, windows-latest)	1m 44s
test-node (latest, ubuntu-latest)	11s
test (v1.x, macOS-latest)	1m 28s
test (v2.x, ubuntu-latest)	2m 17s
wasm (crypto/_wasm)	4s
test (v2.x, windows-latest)	3m 6s
test (v2.x, macOS-latest)	2m 55s
test (canary, ubuntu-latest)	2m 22s
test (canary, windows-latest)	3m 0s
test (canary, macOS-latest)	2m 13s
	21m 47s

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