Support Serde attributes #2269

Job	Run time
maybe-expedite	5s
lint	4m 15s
test (third-party, bincode, stable)	12m 5s
test (third-party, bincode, nightly)	10m 58s
test (third-party, postcard, stable)	12m 16s
test (third-party, postcard, nightly)	11m 5s
test (other, bincode, stable)	28m 25s
test (other, bincode, nightly)	32m 32s
test (other, postcard, stable)	25m 49s
test (other, postcard, nightly)	31m 45s
all-checks	1s
	2h 49m 16s

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