Adds support for "%v" in absl::StrFormat and related functions for numeric types, including integer and floating point values. Users may now specify %v and have the format specifier deduced. Integer values will print according to %d specifications, unsigned values will use %u, and floating point values will use %g. Note that %v does not work for `char` due to ambiguity regarding the intended output. Please continue to use %c for `char`.

PiperOrigin-RevId: 474658166
Change-Id: Iecae39263e368b27232db440535f2bf7da8d863c