[libcxx] chrono::month_weekday should not be default constructible

It was not in P0355R7, nor has it ever been so in a working draft.

Drive-by:
* tests should test something: fix loop bounds so initial value is not >= final value
* calender type streaming tests are useless - let's remove them
* don't declare printf, especially if you don't intend to use it

Differential Revision: https://reviews.llvm.org/D117638