Remove FormatOrString and remaining uses of format()

src/libutil/util.hh

@@ -569,7 +569,7 @@ bool shouldANSI();
    some escape sequences (such as colour setting) are copied but not
    included in the character count. Also, tabs are expanded to
    spaces. */
-std::string filterANSIEscapes(const std::string & s,
+std::string filterANSIEscapes(std::string_view s,
     bool filterAll = false,
     unsigned int width = std::numeric_limits<unsigned int>::max());