Add io_buffer_size to BackupEngineOptions #3803

Job	Run time
build-linux-arm	14m 3s
build-linux	17m 13s
build-fuzzers	8m 38s
build-examples	11m 0s
build-linux-clang10-asan	17m 13s
build-linux-clang10-clang-analyze	17m 17s
build-linux-clang10-ubsan	17m 47s
build-linux-clang13-mini-tsan	24m 40s
build-linux-clang-13-no_test_run	7m 19s
build-linux-clang-no_test_run	12m 5s
build-linux-cmake-mingw	12m 25s
build-linux-cmake-with-benchmark	20m 1s
build-linux-cmake-with-folly	28m 9s
build-linux-cmake-with-folly-coroutines	32m 15s
build-linux-cmake-with-folly-lite-no-test	8m 14s
build-linux-encrypted_env-no_compression	15m 58s
build-linux-gcc-10-cxx20-no_test_run	9m 42s
build-linux-gcc-11-no_test_run	10m 27s
build-linux-gcc-8-no_test_run	9m 26s
build-linux-java	15m 3s
build-linux-java-pmd	12m 31s
build-linux-java-static	12m 14s
build-linux-make-with-folly	28m 33s
build-linux-make-with-folly-lite-no-test	9m 43s
build-linux-mini-crashtest	29m 52s
build-linux-release	14m 24s
build-linux-release-rtti	12m 45s
build-linux-static_lib-alt_namespace-status_checked	19m 15s
build-linux-unity-and-headers	13m 23s
build-macos	17m 55s
build-macos-cmake (true)	52m 52s
build-macos-java	14m 34s
build-macos-cmake (false)	47m 11s
build-macos-java-static	21m 31s
build-macos-java-static-universal	22m 32s
build-windows-vs2019	53m 50s
check-format-and-targets	19s
	11h 32m 19s

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