generateSampleShifts: Simulate sample shifts for each cell state
In immunogenomics/scpost: Simulates single-cell datasets from input data

This function generates linear shifts in each samplefor each cell state. These shifts contribute to the adjusted centroid that is used for simulating PC locations

1	generateSampleShifts(sample_list, sample_vars, s_scale)

`sample_list`	A named list of the sample names e.g. sample1, sample2, etc.
`sample_vars`	A matrix containing the sample_associated variance for each cell state in each PC. These are obtained as output from the "estimatePCVar" function.
`s_scale`	The magnitude of sample-associated gene expression variation the simulated dataset will exhibit. Setting s_scale = 1 will result in realistic levels of sample-associated variation (as derived from parameter estimation of the input dataset). Increasing s_scale results in higher variation, while decreasing s_scale results in lower variation.