fix!: Return originally passed data as select events instead of mutated ones.

[mturoci]

@marek-mihok - can you make a code review and a thorough QA to check if everything works as expected?

Breaking change alert

• The returned event data is now the same as passed in. Prior to this PR, the data could have been mutated eg when scale='time' to timestamps.
• Slight return format change: The events are returned in a flat array instead of a nested ([[]]) array for line, area plots etc.

[marek-mihok]

LGTM @mturoci!

But note that taking into account possible override of idx value (that user specifies idx as a field name) does not make sense since the idx is overiden in refactorData on line 591 anyway:

ds.forEach((d, idx) => d.idx = idx)

You can try replacing value with idx in the plot_events_disabled.py example and see for yourself. Data are plotted with 0,1,2,3,4... indexes regardless of what indexes are specified.

It's worth considering fixing.

[mturoci]

Good point. Not related to the events though so will fix in another commit.