feat(remap): support dropping events when remap fails or is aborted

[JeanMertz]

Dropping on error was previously possible, but undocumented.

This PR also adds an option to drop_on_abort, which defaults to true, and will instruct Vector to drop events when the program is manually aborted through the abort statement.

closes #6720

[jszwedko]

I like it. I think you need to update the benches to use the new struct field name.

[StephenWakely]

Should this actually be pushing the original event? In other words, do we want an abort to abandon any changes made in the script, or should it keep any changes made up to the point abort was called (assuming drop_on_abort is false)?

If we do, I notice that the abort function as actually marked as infallible. Presumable, this would mean either we would have to abandon the check above and clone even if the script is infallible, or we need to mark abort as fallible.

[jszwedko]

This is a good question! My inkling would be to have abort not persist any modifications.

Maybe @binarylogic has an opinion.

[JeanMertz]

My idea was it should. But I’ll defer to your decision

[StephenWakely]

If it does keep the event, then it isn't really doing much more that an if statement.

[jszwedko]

abort says to me that the entire script should be aborted and have similar similar effects as if there were an error: namely that any mutations are discarded.

If we called it return on the other hand, I could see preserving the modifications.

I do agree that an abort that preserves modifications is not significantly different from an if statement wrapping the parts of the script that the user would not like to be executed.

[binarylogic]

The term "abort" feels like it should abort the script and not persist changes. Alternatively, something like "emit" (like we use in Lua) might be better served for preserving changes and exiting early.

[jszwedko]

Noting I mentioned this PR to Ben and he had the good question of whether we need two options for dropping events separately, or if we should just have one: drop_on_abort that applies to both errors and aborts.