[libc++][format] Adds parser std-format-spec.
This implements the generic std.format.spec framework for all types.
The Unicode support will be added in a separate patch.
Implements parts of:
- P0645 Text Formatting
Completes:
- LWG-3242 std::format: missing rules for arg-id in width and precision
- P1892 Extended locale-specific presentation specifiers for std::format
Reviewed By: #libc, ldionne, vitaut
Differential Revision: https://reviews.llvm.org/D103368
GitOrigin-RevId: a04a6ce7726b51c4f503c8de899362bee40d4e04
12 files changed
