Update docs for CompareExchange\<T>

[gewarren]

Fixes #11419.

[Copilot]

Pull Request Overview

This PR updates the XML documentation for the CompareExchange methods by revising type parameter descriptions and summary texts. Key changes include:

• Removing the explicit reference type constraint from the type parameter T.
• Updating summary tags to use consistently.
• Reformulating the remarks section to streamline the note about method overload preference.

Comments suppressed due to low confidence (2)

xml/System.Threading/Interlocked.xml:1344

• The removal of the explicit reference type constraint on T may be intentional; consider adding a brief note explaining this change to clarify the updated usage.

<typeparam name="T">The type to be used for <paramref name="location1" />, <paramref name="value" />, and <paramref name="comparand" />.</typeparam>

xml/System.Threading/Interlocked.xml:2380

• [nitpick] Consider retaining the [!NOTE] markup format for this note to maintain consistency with other documentation sections, if that aligns with the project's style guidelines.

This method overload is preferable to the <xref:System.Threading.Interlocked.Exchange%28System.Object%40%2CSystem.Object%29> method overload, because the latter requires late-bound access to the destination object.