MdePkg: Add deprecated warning to BaseRngLibTimer

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4504

To keep the MdePkg self-contained and avoid dependencies on GUIDs
defined in other packages, the BaseRngLibTimer was moved to the
MdePkg.
Add a constructor to warn and request to use the MdeModulePkg
implementation.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Kun Qin <kun.qin@microsoft.com>

MdePkg/Library/BaseRngLibTimerLib/BaseRngLibTimerLib.inf

@@ -23,6 +23,7 @@
   MODULE_TYPE                    = BASE
   VERSION_STRING                 = 1.0
   LIBRARY_CLASS                  = RngLib
+  CONSTRUCTOR                    = BaseRngLibTimerConstructor
 
 [Sources]
   RngLibTimer.c

MdePkg/Library/BaseRngLibTimerLib/RngLibTimer.c

@@ -13,6 +13,28 @@
 
 #define DEFAULT_DELAY_TIME_IN_MICROSECONDS  10
 
+/**
+  This implementation is to be replaced by its MdeModulePkg copy.
+  The cause being that some GUIDs (gEdkiiRngAlgorithmUnSafe) cannot
+  be defined in the MdePkg.
+
+  @retval EFI_SUCCESS   The constructor always returns EFI_SUCCESS.
+**/
+RETURN_STATUS
+EFIAPI
+BaseRngLibTimerConstructor (
+  VOID
+  )
+{
+  DEBUG ((
+    DEBUG_WARN,
+    "Warning: This BaseRngTimerLib implementation will be deprecated. "
+    "Please use the MdeModulePkg implementation equivalent.\n"
+    ));
+
+  return RETURN_SUCCESS;
+}
+
 /**
  Using the TimerLib GetPerformanceCounterProperties() we delay
  for enough time for the PerformanceCounter to increment.