[libc++][chrono] Implements formatter duration.

Partially implements:
- P1361 Integration of chrono with text formatting
- P2372 Fixing locale handling in chrono formatters
- LWG3270 Parsing and formatting %j with durations

Completes:
- P1650R0 std::chrono::days with 'd' suffix
- LWG3262 Formatting of negative durations is not specified
- LWG3314 Is stream insertion behavior locale dependent when Period::type is micro?

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D134742