feature request: ability to pass through all reads by specifying sample '1.0'

[eboyden]

I would actually prefer that 1.0 be treated as a float (returning all reads) rather than an int, whereas 1 would return a single read. I'd even suggest enforcing this behavior, so that integers are treated as numbers and floats are treated as fractions. This could be used to allow oversampling, e.g. 10 would return 10 reads but 10.0 would oversample 10X.

Originally posted by @eboyden in https://github.com/lh3/seqtk/issues/111#issuecomment-999183357