EmulatorPkg: Fix build failure due to Tftp library removal

EmulatorPkg: Fix build failure due to Tftp library removal

The TFTP command was converted from a NULL class library instance to
a dynamic shell command in commit 0961002352e9.

The ShellLib and FileHandleLib resolutions are moved from
Shell app <LibraryClasses> to [LibraryClasses.common]
because dynamic shell commands implemented as DXE_DRIVER modules
also depend on these libraries.

PcdShellLibAutoInitialize must be set to FALSE for both the shell app
itself and the dynamic shell command modules.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Cc: Andrew Fish <afish@apple.com>