Use GetSourceChainConfig instead of OffRampGetAllSourceChainConfigs #3255

Job	Run time
Integration Tests (Fees Test)	19m 24s
Integration Tests (Token Transfer Test)	19m 28s
Integration Tests (USDC Test)	19m 20s
Integration Tests (OOO Execution Test)	19m 23s
Integration Tests (Messaging Test)	18m 8s
Integration Tests (Fee Boosting Test)	18m 7s
Integration Tests (Batching Test)	19m 26s
Integration Tests (CCIPReader Test)	7m 35s
integration-test-ccip-ocr3	1s
	2h 20m 52s

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