add $UENV_xxx to uenv status output

[jgphpc]

This is a feature request for uenv status to be more verbose.
Currently, it shows:

uenv status

/user-environment:nvhpc
  The compiler toolchains, libraries and tools required for the Cuda Fortran Check.

  modules: available
  views:
    prgenv-nvidia

Can you add UENV_MOUNT_FILE and UENV_MOUNT_POINT to the output ? For example:

uenv status

/user-environment:nvhpc
  The compiler toolchains, libraries and tools required for the Cuda Fortran Check.

  modules: available
  views:
    prgenv-nvidia

UENV_MOUNT_FILE=/scratch/e1000/manitart/myimages/nvhpc_a100.squashfs
UENV_MOUNT_POINT=/user-environment