`Synthesizer`の構造改革をする #2301

Job	Run time
rust-lint	3m 46s
actionlint	17s
rust-unit-test	4m 18s
shellcheck	12s
validate-cargo-lock	25s
build-and-test-java-api (windows-latest)	5m 27s
build-and-test-python-api (windows-latest)	7m 46s
build-and-test-java-api (macos-latest)	5m 49s
build-unix-cpp-example (macos-latest, osx-x64-cpu-cpp-shared)	2m 44s
build-and-test-python-api (macos-latest)	3m 59s
build-and-test-java-api (ubuntu-latest)	2m 49s
build-windows-cpp-example	6m 3s
build-unix-cpp-example (ubuntu-latest, linux-x64-cpu-cpp-shared)	1m 47s
build-and-test-python-api (ubuntu-latest)	2m 42s
c-header	24s
rust-integration-test-strategy-matrix	1s
rust-integration-test (windows-2019, directml)	5m 29s
rust-integration-test (macos-11)	3m 28s
rust-integration-test (ubuntu-20.04)	1m 43s
	59m 9s

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