* op-challenger: Support MT-Cannon in run-trace

* ..

* fix multi_test.go

* annotate metrics with mt-cannon

* preserve prestate encoding; use separate dir for mt-cannon

* Update op-challenger/cmd/run_trace.go
Co-authored-by: Adrian Sutton <adrian@oplabs.co>

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Co-authored-by: Adrian Sutton <adrian@oplabs.co>