NDB$EPOCH, NDB$EPOCH_TRANS and NDB$EPOCH2 ignore delete-delete /
delete-NoSuchRow conflicts as these are not properly handled in a way
that avoids divergence in those algorithms.

NDB$EPOCH2_TRANS should detect these conflicts as :
 i) It uses multiple passes to avoid the batching-related
    problems that the row-based algorithms have.
ii) It uses operation reflection to avoid divergence
    in the cases where an Insert follows a detected delete-delete
    conflict.

This patch modifies the behaviour of NDB$EPOCH2_TRANS to treat
delete-delete conflicts like the other conflict types, and
modifies the existing testcases to provide coverage of this
case.

Actual behaviour for DEL-INS conflicts depends on epoch boundaries
relative to user transaction commits, so the testcases take this
into account, using more programmatic checks than the normal
MTR output comparisons.

Rather than deterministic output, we require that the output is
explained by the measured epoch boundaries, and that the
clusters do not diverge.