OvmfPkg: Rename XenTimerDxe to LocalApicTimerDxe

OvmfPkg: Rename XenTimerDxe to LocalApicTimerDxe

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3711

XenTimerDxe is a local Apic timer driver and it has nothing to do
with Xen. So rename it to LocalApicTimerDxe.

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien@xen.org>
Acked-by: Anthony PERARD <anthony.perard@citrix.com
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>