Update e2e relayer loop test to use start-multi command

[romac]

Crate

n/a

Summary

• Update the end-to-end relayer loop test to use start-multi command instead of start, once Fix pagination for channels cli and reorg the query_txs() #827 is in.
• Do not hardcode channel identifiers in relayer loop test.

Acceptance Criteria

The end-to-test relayer loop test uses the start-multi command.

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