ArmVirtPkg: Fix build failure due to Tftp library removal

ArmVirtPkg: 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
[LibraryClasses.common.UEFI_APPLICATION] to [LibraryClasses.common]
because dynamic shell commands are implemented as DXE_DRIVER modules.

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>
[lersek@redhat.com: extend commit message]
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Build-tested-by: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Julien Grall <julien.grall@linaro.org>