Option to utilize non-equidistant min-max in MinMaxLTTB

[jonasvdd]

This GitHub aims to improve the computational performance of the MinMaxLTTB.

To clarify, MinMaxLTTB currently utilizes the x data in the minmax prefetching step. This causes to create equidistant bins, which is computationally expensive.

Since this MinMax prefecthing tends to use an n_out factor greater than 20, it may be advantageous to consider the MinMax prefetching method for only the y-values (and thus not the x-values) while omitting the equidistant binning.