Add example and tweak C3187 error reference

[Rageking8]

• Update error message (remove space before colon and replace "identifier" with "__func__")
• Add __func__ link and tweak remarks (use "identifier" instead of "macro" as per docs/cpp/func.md)
• Add new example showing 2 possible ways to emit C3187
• Add similar C2457 link under "See also"
• Add "Remarks" heading and update metadata