MdeModulePkg/RegularExpressionDxe: Make oniguruma a submodule in edk2.

Use submodule way to access oniguruma. And upgrade oniguruma
version from v6.9.3 to v6.9.4_mark1.
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2073

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>
Signed-off-by: Shenglei Zhang <shenglei.zhang@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

.pytool/CISettings.py

@@ -144,6 +144,8 @@ class Settings(CiBuildSettingsManager, UpdateSettingsManager, SetupSettingsManag
             "CryptoPkg/Library/OpensslLib/openssl", False))
         rs.append(RequiredSubmodule(
             "UnitTestFrameworkPkg/Library/CmockaLib/cmocka", False))
+        rs.append(RequiredSubmodule(
+            "MdeModulePkg/Universal/RegularExpressionDxe/oniguruma", False))
         return rs
 
     def GetName(self):