Testgen add pkg lock (unicode-org#251)

* Add plural rules to CPP

* Add the Rust datetime fmt code

* Rust datetime fmt and updates to ICU4C and NodeJS (unicode-org#240)

* Add plural rules to CPP

* Starting ICU4X datetime fmt

* DateTime format: Set default timezone explicitly

* Fix formatting

* Added ICU4X timezone computation - not working yet!

* DateTime generator updated to ISO formatted string

* DateTime updates for Node and ICU4C.

* Formatted src/datetimefmt.rs

* Updated using CustomTimeZone in ICU4X date time fmt

* Cargo clippified

* Remove unused function

* Update version to ~1.3

* Add package-lock.json for test generation

* Remove unneeded file