Since fmt 11.0.0, formatter:format() is required to be const.Mark
affected functions as const to stay compatible with fmt 11.
Signed-off-by: Yao Zi <ziyao@disroot.org>
There were two main issues with fmtlib and C++20 mode:
- `fmt::format` defaults to compile-time argument checking and requires
using `fmt::runtime(format_string)` to bypass that.
- `std::format` implementation introduces conflicting declarations and
we have to specify the namespace for all `format`/`format_to` calls.
Other units are all uppercased, so using an uppercased "K" makes it look more consistent (especially when {bandwidthUpBits} or something like that is used).