Add `max_ckpt_keep` for trainer #6316

Job	Run time
Build source distribution	17s
determine-arm64-runner	1s
Build wheels for cp311-manylinux_x86_64	6m 14s
Build wheels for cp311-manylinux_x86_64	5m 58s
Build wheels for cp311-macosx_x86_64	7m 28s
Build wheels for cp311-macosx_arm64	3m 14s
Build wheels for cp311-win_amd64	5m 37s
Build wheels for cp310-manylinux_aarch64	5m 28s
build_pypi_index	10s
build_docker (12)	3m 56s
build_docker (_cu11, 11)	3m 42s
upload_pypi	0s
deploy_pypi_index	0s
Pass testing build wheels	3s
	42m 8s

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