Keeps rows with Freq >= umi_cutoff in @GTsummary.filtered, enforces a minimum
number of rows per variant, updates @V.fitered, and rebuilds matrices and depth matrix.
Usage
filter_redeemR_by_UMI(
redeemR_obj,
umi_cutoff = 2,
min_cells_per_variant = 2,
QualifiedTotalCts = NULL,
filter_name = NULL
)