Aggregate SecretConnection chunks with unmarshal protobuf retry #1350

Job	Run time
Check	3m 21s
Build (stable)	3m 18s
Rustfmt	12s
Build (1.74.0)	4m 21s
Clippy	1m 32s
Test Suite (stable)	4m 55s
Test Suite (1.74.0)	5m 12s
Validate against test harness	4m 11s
	27m 2s

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