Add enumeration values for DebugType in XSD

[drewnoakes]

Context

The DebugType property has a set of expected values, and is not just a plain text property.

Currently completion on the DebugType property offers no guidance:

Changes Made

This change adds those values so they appear in completion. It also documents that pdbonly is equivalent to full in recent compilers.

Testing

None.

Notes

None.

[rainersigwald]

LGTM. We're past localization freeze in our repo but not VS where this will actually be localized so we can take this for 17.0.

Can we get a quick look from someone on @dotnet/roslyn-compiler, since this is a C#/VB option?

[drewnoakes]

@rainersigwald I'll leave it to you good folks to determine when this should be merged. Thanks.

[rainersigwald]

@drewnoakes The test failures look legitimate to me--they're in XSD validation. Can you take a look please?

[rainersigwald]

This code has been commented out since time immemorial:

msbuild/src/MSBuild.UnitTests/ProjectSchemaValidationHandler_Tests.cs

Lines 187 to 192 in f566ba1

	//ProjectSchemaValidationHandler.VerifyProjectSchema
	// (
	// projectFilename,
	// msbuildTempXsdFilenames[0],
	// @"c:\"
	// );

But if it wasn't, you would have gotten this test error instead of "expected true" or whatever:

Message: 
    Microsoft.Build.CommandLine.InitializationException : C:\Users\raines\AppData\Local\Temp\4ghowcq5.bch\MSBuild\Microsoft.Build.CommonTypes.xsd(1255,6): Schema validation error : MSBUILD : MSB1046: The schema "C:\Users\raines\AppData\Local\Temp\4ghowcq5.bch\Microsoft.Build.xsd" is not valid. The type attribute cannot be present with either simpleType or complexType.

  Stack Trace: 
    InitializationException.Throw(String message, String invalidSwitch) line 186
    ProjectSchemaValidationHandler.ThrowInitializationExceptionWithResource(String projectFile, Int32 fileLine, Int32 fileEndLine, Int32 fileColumn, Int32 fileEndColumn, String resourceName, Object[] args) line 217
    ProjectSchemaValidationHandler.VerifyProjectSchema(String projectFile, String schemaFile) line 156
    ProjectSchemaValidationHandler.VerifyProjectSchema(String projectFile, String schemaFile, String binPath) line 67
    ProjectSchemaValidationHandlerTest.VerifyValidProjectSchema() line 187

[rainersigwald]

Pushed a fix.