MdeModulePkg: Define the VariablePolicyLib

https://bugzilla.tianocore.org/show_bug.cgi?id=2522

VariablePolicy is an updated interface to
replace VarLock and VarCheckProtocol.

Add the VariablePolicyLib library that implements
the portable business logic for the VariablePolicy
engine.

Also add host-based CI test cases for the lib.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Bret Barkelew <brbarkel@microsoft.com>
Signed-off-by: Bret Barkelew <brbarkel@microsoft.com>
Reviewed-by: Dandan Bi <dandan.bi@intel.com>
Acked-by: Jian J Wang <jian.j.wang@intel.com>

MdeModulePkg/MdeModulePkg.ci.yaml

@@ -104,7 +104,9 @@
             "FVMAIN",
             "VARCHECKPCD",
             "Getxx",
-            "lzturbo"
+            "lzturbo",
+            "musthave",
+            "canthave"
         ],
         "AdditionalIncludePaths": [] # Additional paths to spell check relative to package root (wildcards supported)
     }