make `range.tf` and `as.numeric.tf` compatible with `scales`

[fabian-s]

.. so that ggplot2-functions work as expected once r-lib/scales#480 is done.

[fabian-s]

wait for ggplot2 milestone 4.0

[fabian-s]

continues to break because of out-of-bounds computations:

Browse[1]> scales[[1]]$oob
<ggproto method>
  <Wrapper function>
    function (...) 
oob(...)

  <Inner function (f)>
    function (x, range = c(0, 1), only.finite = TRUE) 
{
    force(range)
    finite <- if (only.finite) 
        is.finite(x)
    else TRUE
    x[finite & x < range[1]] <- NA_real_
    x[finite & x > range[2]] <- NA_real_
    x
}
Browse[1]> x < 2
Error in vec_compare(e1, e2) : 
  Can't combine `..1` <tfd_reg> and `..2` <double>.
Browse[1]> x[1] < x[2]
Error in vec_proxy_compare(x = x) : 
  `vec_proxy_compare.tfd_reg()` not supported.