OvmfPkg: Create initial version of PlatformInitLib

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3863

There are 3 variants of PlatformPei in OvmfPkg:
 - OvmfPkg/PlatformPei
 - OvmfPkg/XenPlatformPei
 - OvmfPkg/Bhyve/PlatformPei/PlatformPei.inf
These PlatformPeis can share many common codes, such as
Cmos / Hob / Memory / Platform related functions. This commit
(and its following several patches) are to create a PlatformInitLib
which wraps the common code called in above PlatformPeis.

In this initial version of PlatformInitLib, below Cmos related functions
are introduced:
 - PlatformCmosRead8
 - PlatformCmosWrite8
 - PlatformDebugDumpCmos

They correspond to the functions in OvmfPkg/PlatformPei:
 - CmosRead8
 - CmosWrite8
 - DebugDumpCmos

Considering this PlatformInitLib will be used in SEC phase, global
variables and dynamic PCDs are avoided. We use PlatformInfoHob
to exchange information between functions.

EFI_HOB_PLATFORM_INFO is the data struct which contains the platform
information, such as HostBridgeDevId, BootMode, S3Supported,
SmmSmramRequire, etc.

After PlatformInitLib is created, OvmfPkg/PlatformPei is refactored
with this library.

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>
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>

OvmfPkg/OvmfPkg.dec

@@ -113,6 +113,10 @@
   #
   TdxMailboxLib|Include/Library/TdxMailboxLib.h
 
+  ##  @libraryclass  PlatformInitLib
+  #
+  PlatformInitLib|Include/Library/PlatformInitLib.h
+
 [Guids]
   gUefiOvmfPkgTokenSpaceGuid            = {0x93bb96af, 0xb9f2, 0x4eb8, {0x94, 0x62, 0xe0, 0xba, 0x74, 0x56, 0x42, 0x36}}
   gEfiXenInfoGuid                       = {0xd3b46f3b, 0xd441, 0x1244, {0x9a, 0x12, 0x0, 0x12, 0x27, 0x3f, 0xc1, 0x4d}}