[3.1] Some overlooked credscan fixes

[danmoseley]

@aik-jahoda this is needed in 2.1, 5.0 and main as well.

I'll let CI run this test..

[aik-jahoda]

Interesting. I didn't seen this as a problem during local run and I can't reproduce the bugs now. Not sure if we need this change.

[danmoseley]

I was using 2.2.5. Does that repro it for you?

[aik-jahoda]

5.0 - dotnet/runtime#50120
6.0 - dotnet/runtime#50230
2.1 - #43058

[danmoseley]

I'll let you handle merging this

[danmoseley]

    System.Xml.Tests.CNameTableTestModule.RunTests(testCase: Get Valid Super String) [FAIL]
      OLEDB.Test.ModuleCore.CTestException : objTest3 is  null
      Expected: `True`
      Actual: `False`
      Result: 0
      
      Stack Trace:
        /_/src/System.Private.Xml/tests/Readers/NameTable/XmlNameTable.cs(355,0): at System.Xml.Tests.TCRecordNameTableGet.Variation_10()
        /_/src/Common/tests/System/Xml/ModuleCore/cvariation.cs(77,0): at OLEDB.Test.ModuleCore.CVariation.Execute()
        /_/src/Common/tests/System/Xml/ModuleCore/ctestcase.cs(132,0): at OLEDB.Test.ModuleCore.CTestCase.<>c__DisplayClass7_1.<TestCases>b__0()
        /_/src/Common/tests/System/Xml/ModuleCore/XunitTestCase.cs(34,0): at OLEDB.Test.ModuleCore.XunitTestCase.Run()
        /_/src/System.Private.Xml/tests/Readers/NameTable/CNameTableTestModule.cs(17,0): at System.Xml.Tests.CNameTableTestModule.RunTests(XunitTestCase testCase)

unrelated