smarie/python-pytest-cases: 2.4.0 - various fixes for test ids and lazy values

is_lazy is now part of public API, and _LazyValue now has a cache mechanism like _LazyTuple. Fixes #143 @parametrize: custom ids are now correctly taken into account when a single lazy_valueis used for a tuple of parameters. This issue could be seen also with @parametrize_with_cases: idgen does not seem to be taken into account when cases are unpacked into a tuple. Fixes #144. Empty case ids are now replaced with '' to avoid ambiguous interpretation of test ids. Fixes #142. See documentation page for details