feat: limit the number of messages in prepare proposal #6018

Job	Run time
goreleaser / goreleaser-check	1m 39s
lint / golangci-lint	2m 52s
lint / yamllint	7s
markdown-linter / markdown-link-check	2m 34s
markdown-linter / markdown-lint	9s
test / test-short	4m 13s
test / test	11m 52s
test / test-coverage	5m 17s
test / test-fuzz	5m 40s
test / test-race	13m 54s
lint / hadolint / hadolint	5s
goreleaser / goreleaser	0s
	48m 22s

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