op-program: Introduce RetryingL2Sources and use it to make prefetcher somewhat multi-L2 capable (#13718)

* op-program: Introduce L2Sources to combine info for multiple L2s.

* op-program: Plumb L2Sources in

* op-e2e: Use actual chain ID, not hte test place holder.

* op-program: Use correct chain ID for rexec and prevent duplicate RPC urls for same chain

* op-program: Fix test to use chain ID that is actually configured in the test