Add FileOutputStream::close #542

Job	Run time
rust_ci (macos-latest, stable)	38s
rust_ci (macos-latest, beta)	1m 4s
rust_ci (macos-latest, nightly)	1m 6s
rust_ci (ubuntu-latest, stable)	43s
rust_ci (ubuntu-latest, beta)	1m 30s
rust_ci (windows-latest, stable)	2m 28s
rust_ci (windows-latest, nightly)	2m 41s
rust_ci (ubuntu-latest, nightly)	1m 20s
rust_ci (windows-latest, beta)	2m 41s
	14m 11s

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