Add `*Record` ProtoBuf messages and corresponding serde functions. #6256

Job	Run time
Build, test and upload wheel	1m 29s
Framework / bare	1m 35s
Framework / bare-https	1m 17s
Strategy / FedMedian	1m 12s
Framework / jax	2m 8s
Strategy / FedTrimmedAvg	1m 7s
Framework / pytorch	4m 22s
Strategy / QFedAvg	1m 12s
Framework / tensorflow	3m 1s
Strategy / FaultTolerantFedAvg	1m 9s
Framework / tabnet	2m 43s
Strategy / FedAvgM	1m 12s
Framework / opacus	3m 30s
Strategy / FedAdam	1m 15s
Framework / pytorch-lightning	2m 33s
Strategy / FedAdagrad	1m 18s
Framework / mxnet	1m 39s
Strategy / FedYogi	1m 12s
Framework / scikit-learn	2m 17s
Framework / fastai	3m 53s
Framework / pandas	1m 39s
	41m 43s

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