ShellPkg/ShellCommandLib: Update DumpHex to print {|}~

ShellPkg/ShellCommandLib: Update DumpHex to print {|}~

ASCII characters {|}~ should be printed by DumpHex. The problem is that
if you have a string like

    {xizzy}~{foo|bar}~{quux}

in the dumped data, it will not appear as such in the *-delimited ASCII
column to the right, but as

    .xizzy...foo.bar...quux.

which is less than ideal.

Most of the commit message was inspired by/shamelessly stolen from
Laszlo's example:

    https://lists.01.org/pipermail/edk2-devel/2017-April/010266.html

Cc: Jaben Carsey <jaben.carsey@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Westfahl <jeff.westfahl@ni.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>