util: add %i and %f formatting specifiers

This change brings formatting specifiers available in `util.format` and
consequently, `console.*` closer to what is supported in all major
browsers.

- `%i` is introduced to format integer values.
- `%f` is introduced to format floating point values.

Fixes: https://github.com/nodejs/node/issues/10292
PR-URL: https://github.com/nodejs/node/pull/10308


Reviewed-By: James M Snell <jasnell@gmail.com>