[intl] Expose the ICU NumberRangeFormatter

[stof]

Description

ICU4C has a NumberRangeFormatter API allowing to format a range between 2 numbers based on the convention of each locale.

It would be great to provide a PHP API based on it.

[stof]

This was first mentioned by @Ayesh in #18346 (comment)

[BogdanUngureanu]

According to the docs, that class (and its C equivalent) are stable since ICU 63 68. Unfortunately, PHP should support ICU 57.1 and up. The version was bumped recently I believe.

I implemented IntlListFormatter because the base functionality (without OR and UNITS) was supported in 57.

[nielsdos]

It's still possible to support it, with conditional compilation. It's not unheard of making some classes / functions only available for recent lib versions.

[nielsdos]

@BogdanUngureanu Still interested in this? Otherwise I might give it a try.

[BogdanUngureanu]

@nielsdos yeah, I would like to work on it. I was thinking today or tomorrow