Use util-format-x for util.format and util.formatWithOptions

Pending the resolution of https://github.com/Xotic750/util-format-x/issues/2, we should use that package as it is the most up to date `util.format` implementation for the browser.

Start by reading the linked util-format-x issue 2 and reviewing the current util.format and util.formatWithOptions implementations in this repository. Once that upstream issue is resolved, replace both implementations with util-format-x and verify that the browser module preserves the expected formatting behavior.

索引モデルが issue の本文から書いたものです。