This commit updates our Date/Time formatting/printing tests to
demonstrate that the use of fallback patterns can help mitigate
locale-based parsing/formatting issues beginning with JDK 20.
The documentation within the tests is intentionally rather thorough for
two reasons:
1. We need to understand exactly what it is we are testing and why the
tests are written that way.
2. We may re-use parts of the documentation and examples in forthcoming
documentation that we will provide to users.
See gh-33151
bbbb7c396e