improve: rework `VoiceModel` #2852

Job	Run time
actionlint	18s
rust-integration-test-strategy-matrix	1s
c-header	55s
rust-lint	3m 32s
rust-unit-test	4m 16s
shellcheck	19s
validate-cargo-lock	25s
build-and-test-java-api (windows-latest)	6m 0s
build-and-test-python-api (windows-latest)	5m 35s
build-and-test-java-api (macos-latest)	2m 41s
build-and-test-python-api (macos-latest)	3m 4s
build-and-test-java-api (ubuntu-latest)	2m 53s
build-unix-cpp-example (macos-latest, osx-x64-cpu-cpp-shared)	1m 33s
build-unix-cpp-example (ubuntu-latest, linux-x64-cpu-cpp-shared)	1m 37s
build-and-test-python-api (ubuntu-latest)	3m 0s
build-windows-cpp-example	3m 58s
rust-integration-test (macos-12)	5m 9s
rust-integration-test (ubuntu-20.04)	1m 32s
	46m 48s

Provide feedback