Unify references to types in XML comments

[michael-hawker]

Based on a comment in #3434, we should do a better job of consistency in our XML comments.

We should do an audit and then add guidance in our contributor docs.

Side note - we should unify the way we display langwords in XML comments throughout the repository. Right now we have some displayed as plain text, some as inline markdown code (true), some as XML code blocks (<c>true</c>), some as XML langwords (langword="true").

Originally posted by @Sergio0694 in #3434 (comment)

Hello michael-hawker, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌

[michael-hawker]

Another example: #3434 (comment)

Side note, ideally all these type references should be proper XML refs, for consistency and also to allow devs to just CTRL + click into any of these to read more about them through the VS jump to definition feature.