StandaloneMmPkg/Core: Limit FwVol encapsulation section recursion

MmCoreFfsFindMmDriver() is called recursively for encapsulation sections.
Currently this recursion is not limited. Introduce a new PCD
(fixed-at-build, or patchable-in-module), and make MmCoreFfsFindMmDriver()
track the section nesting depth against that PCD.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Wei6 Xu <wei6.xu@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

StandaloneMmPkg/Core/Dispatcher.c

@@ -53,11 +53,6 @@ typedef struct {
 // Function Prototypes
 //
 
-EFI_STATUS
-MmCoreFfsFindMmDriver (
-  IN  EFI_FIRMWARE_VOLUME_HEADER  *FwVolHeader
-  );
-
 /**
   Insert InsertedDriverEntry onto the mScheduledQueue. To do this you
   must add any driver with a before dependency on InsertedDriverEntry first.