UefiCpuPkg/PiSmmCpuDxeSmm: Introduce page table pool mechanism

Introduce page table pool mechanism for smm page table to simplify
page table memory management and protection. This mechanism has been
used in DxeIpl. The basic idea is to allocate a bunch of continuous
pages of memory in advance, and all future page tables consumption
will happen in those pool instead of system memory.
Since we have centralized page tables, we only need to mark all page
table pools as RO, instead of searching page table memory layer by
layer in smm page table. Once current page table pool has been used
up, another memory pool will be allocated and the new pool will also
be set as RO if current page table memory has been marked as RO.

Signed-off-by: Dun Tan <dun.tan@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>

UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c

@@ -1322,36 +1322,6 @@ ConfigSmmCodeAccessCheck (
   }
 }
 
-/**
-  This API provides a way to allocate memory for page table.
-
-  This API can be called more once to allocate memory for page tables.
-
-  Allocates the number of 4KB pages of type EfiRuntimeServicesData and returns a pointer to the
-  allocated buffer.  The buffer returned is aligned on a 4KB boundary.  If Pages is 0, then NULL
-  is returned.  If there is not enough memory remaining to satisfy the request, then NULL is
-  returned.
-
-  @param  Pages                 The number of 4 KB pages to allocate.
-
-  @return A pointer to the allocated buffer or NULL if allocation fails.
-
-**/
-VOID *
-AllocatePageTableMemory (
-  IN UINTN  Pages
-  )
-{
-  VOID  *Buffer;
-
-  Buffer = SmmCpuFeaturesAllocatePageTableMemory (Pages);
-  if (Buffer != NULL) {
-    return Buffer;
-  }
-
-  return AllocatePages (Pages);
-}
-
 /**
   Allocate pages for code.