[libc++][format] Adds formatter pointer.

This implements the last required formatter specialization.

Completes:
- LWG 3251 Are std::format alignment specifiers applied to string arguments?
- LWG 3340 Formatting functions should throw on argument/format string mismatch in §[format.functions]
- LWG 3540 §[format.arg] There should be no const in basic_format_arg(const T* p)

Implements parts of:
- P0645 Text Formatting

Depends on D114001

Reviewed By: ldionne, vitaut, #libc

Differential Revision: https://reviews.llvm.org/D115988

NOKEYCHECK=True
GitOrigin-RevId: 787ccd345cbb3a569ba751580bb806552b4b6e57
diff --git a/include/module.modulemap b/include/module.modulemap
index c940a6d..90fae9b 100644
--- a/include/module.modulemap
+++ b/include/module.modulemap
@@ -506,6 +506,7 @@
       module formatter_floating_point { private header "__format/formatter_floating_point.h" }
       module formatter_integer        { private header "__format/formatter_integer.h" }
       module formatter_integral       { private header "__format/formatter_integral.h" }
+      module formatter_pointer        { private header "__format/formatter_pointer.h" }
       module formatter_string         { private header "__format/formatter_string.h" }
       module parser_std_format_spec   { private header "__format/parser_std_format_spec.h" }
     }