MdeModulePkg: Update Dxe to handle unaccepted memory type

MdeModulePkg: Update Dxe to handle unaccepted memory type

RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3937

Unaccepted memory is a kind of new memory type,
CoreInitializeGcdServices() and CoreGetMemoryMap() are updated to handle
the unaccepted memory type.

Ref: microsoft/mu_basecore@97e9c31

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Signed-off-by: Min Xu <min.m.xu@intel.com>