Support inflection functionality into icu::message2

[FrankYFTang]

icu::message2 provide two intreface to integrate additional functionality into MF2
icu::message2::FormatFactory and
icu::message2::SelectorFactory

This issue aim to add concrete implementations of that two interface from inflectino library so the caller can easily adopt the functionality inside inflection into ICU4C MF2.

This a sub task of #61

[FrankYFTang]

reopen to add more unit tests in data driven fashion