feat: download blobs in `PendingBlocks` #2897

Job	Run time
Lint	1m 49s
Build native libraries	13s
Download Beacon Node OAPI	6s
Download spectests	8s
Start and stop the node	4m 5s
Build project	3m 53s
Run spec-tests (capella, minimal)	6m 54s
Test	3m 20s
Run spec-tests (capella, general)	5m 11s
Run spec-tests (capella, mainnet)	7m 8s
Run spec-tests (deneb, minimal)	7m 26s
Run spec-tests (deneb, general)	4m 56s
Run spec-tests (deneb, mainnet)	7m 19s
All spec-tests passed	1s
	52m 29s

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