Allow independent assignment of axis tick mark length

[helen-zhu]

It can be useful to independently assign the length of tick marks on axes (e.g. when the labels are too crowded).

Currently, yaxis.tck takes a vector of length 1 or 2 which controls the tick mark length on the left/right (on create.heatmap but probably generalizable) but presumably, this would be better as two parameters yaxis.tck and yaxis.right.tck where each takes a vector of length 1 or length(yat) which can independently control the length of each tick mark. Also useful for xaxis.tck.

This can be done using scale.components in Lattice and currently, plots can be modified post-creation to accommodate this but would be nice to have as a feature:

https://www.rdocumentation.org/packages/latticeExtra/versions/0.6-29/topics/scale.components