improve: rework `VoiceModel` #2853

Job	Run time
actionlint	21s
rust-lint	4m 21s
shellcheck	14s
build-and-test-java-api (windows-latest)	7m 44s
build-and-test-python-api (windows-latest)	5m 23s
build-and-test-java-api (macos-latest)	3m 4s
build-and-test-python-api (macos-latest)	3m 44s
build-and-test-java-api (ubuntu-latest)	3m 4s
build-and-test-python-api (ubuntu-latest)	7m 50s
build-unix-cpp-example (macos-latest, osx-x64-cpu-cpp-shared)	1m 33s
build-windows-cpp-example	3m 59s
build-unix-cpp-example (ubuntu-latest, linux-x64-cpu-cpp-shared)	1m 33s
c-header	46s
rust-integration-test-strategy-matrix	1s
rust-unit-test	4m 30s
validate-cargo-lock	23s
rust-integration-test (macos-12)	2m 43s
rust-integration-test (ubuntu-20.04)	1m 33s
	52m 46s

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