typo
Refactor irrelevant failure pruning for element events.

Prune individual failures instead of entire events.

This avoid pruning events that may have interesting failures if they
also include an irrelevant one.
Element log entries now have the array MDefinition address as argument.
Remove erroneous comment.

If two operations have the same location (which include bytecode
offset), they have to be the same instruction, and can't be different
kinds of operations.
Preserve more info across merging.

Necessary for subsequent merging / pruning passes.
Add a second locality merging pass for element reports.

Merge near misses from the same script that affect the same array.
Switch the second merging pass to merge all within a script.

See comment for rationale.