Drop explicit calls to chain.GetTx from txs execution paths #6279

Job	Run time
Fuzz	13m 8s
Unit (macos-12)	16m 1s
Unit (ubuntu-20.04)	6m 32s
e2e	10m 15s
Unit (ubuntu-22.04)	6m 47s
e2e_existing_network	3m 41s
Unit (windows-2022)	11m 52s
Unit (custom-arm64-focal)	12m 37s
Unit (custom-arm64-jammy)	11m 51s
Protobuf Lint	6s
Up-to-date protobuf	40s
Up-to-date go.mod and go.sum	15s
Up-to-date mocks	2m 11s
Lint	3m 15s
Build Antithesis xsvm images	8m 11s
Image build	10m 34s
Upgrade	3m 24s
Build Antithesis avalanchego images	5m 32s
	2h 6m 52s

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