Optimize json marshaller #3468

Job	Run time
check-s3-related-changes	1m 4s
s3-regression-tests-download	30m 59s
s3-regression-tests-upload-crt	8m 22s
s3-regression-tests-control-plane	6m 22s
s3-regression-tests-upload-sync	9m 54s
s3-regression-tests-upload-multi	7m 53s
s3-regression-tests-upload-async	24m 27s
	1h 29m 1s

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