Fix UseCompilerGeneratedDocXmlFile default value

[ViktorHofer]

Fixes what was reported in #105974 (comment) by @michaelgsharp (thanks!)

Regressed with #94234

For now suppress the undocumented public APIs that got added since the property got switched to the wrong default. These public APIs are tracked via #105974.

@carlossanlop @ericstj please take a look and merge

[carlossanlop]

For Tensors, instead of pragma disables, can we instead disable the property in the csproj? The APIs are actively getting documented, so we should keep it simple and easy to activate, as well as try to avoid a bunch of merge conflicts #106084

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[ViktorHofer]

Disabling the property in the project file is probably not what we want. That stops the compiler from emitting CS1591 for new API that is getting added or from validating that existing documented API stays documented.

It should be trivial for @michaelgsharp to react to this change in his PR (search for '1591' and remove). If his PR gets merged first, then this PR can be simplified.

[ericstj]

Looks like this is causing an error due to it's use of a PNSE.

[ericstj]

LGTM, once we get System.Speech working correctly. Might have to manually override the check on this one to allow for no XML for the PNSE (better than no docs at all)