Elango Cheran

In order to "modernize" the `BreakIterator` API, this PR introduces a new wrapper using a more convenient, modern API design around a `Segmenter` interface. A few of the goals that...

Similar to #805, we also agreed that we wanted to collect feedback from the ICU-TC on MF2. Similar to #782, we might also want to ask ICU4X-TC for feedback as...