Toggle subsampling of tick labels when tickmode="array"

[alanocallaghan]

It would be useful to allow users to specify tick values and tick labels, and then have plotly perform the same subsampling of labels that it performs when tickmode="auto".

This would be useful because it is important to use common co-ordinates for subplots. This sometimes requires mapping categorical variables to numeric values in order to align with a numeric axis.

I imagine this may not be a massive fix; if you'd like and don't mind pointing in the right direction, I would be happy to implement this

[etpinard]

Duplicate of #1618