Some cleanup around PInvokeStaticSigInfo (#52232)

Author: elinor-fung

src/coreclr/vm/binder.cpp

@@ -1038,8 +1038,7 @@ void CoreLibBinder::CheckExtended()
         else
         if (pMD->IsNDirect())
         {
-            PInvokeStaticSigInfo sigInfo;
-            NDirect::PopulateNDirectMethodDesc((NDirectMethodDesc *)pMD, &sigInfo);
+            NDirect::PopulateNDirectMethodDesc((NDirectMethodDesc *)pMD);
 
             if (pMD->IsQCall())
             {

src/coreclr/vm/classcompat.cpp

@@ -3311,7 +3311,7 @@ HRESULT MethodTableBuilder::FindMethodDeclarationForMethodImpl(
             IfFailRet(pMDInternalImport->GetNameAndSigOfMemberRef(tkMethod, &pSig, &cSig, &szMember));
 
             if (isCallConv(
-                MetaSig::GetCallingConvention(NULL, Signature(pSig, cSig)),
+                MetaSig::GetCallingConvention(Signature(pSig, cSig)),
                 IMAGE_CEE_CS_CALLCONV_FIELD))
             {
                 return VLDTR_E_MR_BADCALLINGCONV;

src/coreclr/vm/compile.cpp

@@ -5735,7 +5735,7 @@ void CEEPreloader::GenerateMethodStubs(
         {
             NDirectMethodDesc* pNMD = (NDirectMethodDesc*)pMD;
             PInvokeStaticSigInfo sigInfo;
-            NDirect::PopulateNDirectMethodDesc(pNMD, &sigInfo);
+            NDirect::InitializeSigInfoAndPopulateNDirectMethodDesc(pNMD, &sigInfo);
             pStubMD = NDirect::GetILStubMethodDesc((NDirectMethodDesc*)pMD, &sigInfo, dwNGenStubFlags);
         }
 #ifdef FEATURE_COMINTEROP