This patch fixes warnings and errors that come up when running the
benchmarks as part of the test suite. It also adds the necessary Lit
annotations to make it pass in various configurations and increases the
portability of the benchmarks.
This patch is the start of a series to improve the speed of std::format,
std::format_to, std::format_to_n, and std::formatted_size.
This is mostly achieved by changing the __output_buffer class. This new
__output_buffer class also makes it easier to implement buffering for
P3107R5 "Permit an efficient implementation of std::print"
This is an intermediate and fairly mechanical step towards unifying the
benchmarks with the rest of the test suite. Moving this around requires
a few changes, notably making sure we don't throw a wrench into the
discovery process of the normal test suite. This won't be a problem
anymore once benchmarks are taken into account by the test setup out of
the box.
