Homogenize classifications of mempool conflict errors

Context

Change the classification of the mempool error Operation_replacement to branch_delayed, to match the classification of Operation_conflict. This means that now, when two operations conflict, the one that is not selected will have the same error classification regardless of the order in which the operations were received or injected.

Fixes #5198 (closed)

Manually testing the MR

CI

Checklist

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