feat(csharp): XML encode contents of <summary> and <example><code> code comments

[Swimburger]

When < and > are used inside of summary or code example XML docs, the XML doc is invalid. This PR HTML encodes the contents before putting it in the XML doc.

This will also XML encode other characters which aren't really necessary, like ", but IDEs continue to show the XML docs correctly.

[github-actions[bot]]

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[dcb6]

This part of the description is no longer accurate, correct?

This will also XML encode other characters which aren't really necessary, like ", but IDEs continue to show the XML docs correctly.

[Swimburger]

This part of the description is no longer accurate, correct?

This will also XML encode other characters which aren't really necessary, like ", but IDEs continue to show the XML docs correctly.

Correct!