graph: Add retries for FirehoseEndpoint::load_blocks_by_numbers #9311

Job	Run time
Subgraph Runner integration tests	3m 54s
Run integration tests	4m 57s
Clippy linting	1m 2s
Build in release mode	1m 2s
Check rustfmt style	6s
Run unit tests	8m 28s
	19m 29s

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