Accept variable-length batch prompts for Whisper #2919

Job	Run time
build-and-test-cpp-aarch64 (openblas)	5m 19s
build-and-test-cpp-x86_64 (ubuntu-20.04, mkl)	10m 6s
build-and-push-docker-images	29m 47s
build-and-test-cpp-x86_64 (ubuntu-20.04, dnnl)	5m 48s
build-python-wheels (ubuntu-20.04, auto64)	35m 53s
build-python-wheels (windows-2019, auto64)	44m 30s
check-python-style	9s
build-python-wheels (ubuntu-20.04, aarch64)	1h 21m 6s
build-python-wheels (macos-12, arm64)	7m 52s
build-and-deploy-docs	35s
test-python-wheels (ubuntu-20.04)	6m 33s
test-python-wheels (windows-2019)	4m 8s
publish-python-wheels-on-pypi	0s
	3h 51m 46s

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