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ARROW-15520: [C++] Qualify `arrow_vendored::date::format()` for C++20 compatibility

As explained in ARROW-15520, these unqualified calls to `format()` are ambiguous in the C++20 Standard.

The `using`-declaration `using arrow_vendored::date::format;` makes the compiler consider the desired overload, but it doesn't automatically win. Argument-Dependent Lookup also considers `std::format()` because the arguments are `std::chrono::duration` types (and `<chrono>` includes `<format>` in MSVC's implementation). A very recent change to `std::format()`'s signature in a C++20 Defect Report makes it an equally good match as the desired `arrow_vendored::date::format()` overload, so the compiler emits an ambiguity error.

The fix is simple, although slightly verbose - the code simply needs to explicitly qualify each call, in order to defend against Argument-Dependent Lookup. The fix is also perfectly backwards-compatible (i.e. it works in previous Standard versions, and with all other platforms).

(Also as mentioned in ARROW-15520, although this requires building Apache Arrow with non-default settings to use the latest C++ Standard version, this change is good for future-proofing and will make it easier for the MSVC team to continue validation that prevents toolset regressions that could affect Apache Arrow and other projects.)

Closes #12317 from StephanTLavavej/cxx20-format

Lead-authored-by: Stephan T. Lavavej <stl@microsoft.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Co-authored-by: Stephan T. Lavavej <stl@nuwen.net>
Signed-off-by: Antoine Pitrou <antoine@python.org>