test: improve observable ICU behaviour coverage
Refs: https://github.com/nodejs/node/issues/42440
Test for bundled full-icu
and its intergation with Node.
Starting from v70, it caches locale and ignores attempts to mutate process.env
in runtime (for example, to normalize Date
stringification). This test gives an example of observable results and tests if this behaviour is kept.
Tests are performed for full-icu >=71.x.