ShellPkg: Add NetworkPkg/NetworkPkg.dec as the package dependency

ShellPkg: Add NetworkPkg/NetworkPkg.dec as the package dependency

NetLib will be moved from MdeModulePkg and NetworkPkg.
So, the module that consumes NetLib need to depend on NetworkPkg.dec.

Signed-off-by: Liming Gao <liming.gao@intel.com>
Cc: Zhichao Gao <zhichao.gao@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>