feat: download blobs in `PendingBlocks` #2869

Job	Run time
Lint	1m 48s
Build native libraries	16s
Download Beacon Node OAPI	6s
Download spectests	5s
Run spec-tests (capella, minimal)	7m 20s
Run spec-tests (capella, general)	4m 44s
Build project	4m 34s
Run spec-tests (capella, mainnet)	6m 52s
Test	3m 49s
Start and stop the node	4m 26s
Run spec-tests (deneb, minimal)	6m 52s
Run spec-tests (deneb, general)	4m 58s
Run spec-tests (deneb, mainnet)	4m 33s
All spec-tests passed	1s
	50m 24s

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