Remove fmt in favor of std::format, upgrade spdlog to current version

[Holt59]

Some details:

• The include path from spdlog does NOT include spdlog anymore which is why #include are now spdlog/spdlog.h rather than simply spdlog.h.
• std::ostream& operator<< operators have been converted specializations of std::formatter - almost everything can be found in the formatters.h header:
  • Specializations for wide chars on non-wide char format (same as before).
  • Specialization for PCUNICODE_STRING.
  • Specialization for pointers - This was need as std::format does not natively support pointers other than void* and const void*.
  • Specialization for Wrap<NTSTATUS> and Wrap<DWORD>.
  • Removed every notion of Wrap<STR> (STR being any kind of string) as this was not doing anything different than the standard formatters. The only use cases for Wrap are now NTSTATUS and DWORD.
  • Specialization for usvfs::UnicodeString.
• Some refactoring for fmt::MemoryWriter using std::format_to.
• toHex and SeverityShort functions were simply removed since these are not used anywhere and annoying to convert.
• Update for spdlog sinks:
  • Extra headers are included when needed.
  • Switch from the custom null sink to the spdlog one.
  • Updated the shmsink.
• Change many usage of path::u8string() to simply path::string() because in C++20 both are different, and it is very complicated to mix both (and support for u8string is very poor).

[Al12rs]

Thanks for all the work here. Good to be on c++20. A lot of nice cleanup here

[Holt59]

This file contains most formatters for std::format - These are basically the ones from loghelpers before. I tried to reduce the amount of copy/paste so most formatters forward to other formatters for the sake of readibility.

There is not formatters for wrapped strings because those were not doing anything more than the standard formatters.

The formatter for USVFS own UnicodeString is in a separate file.

[Holt59]

Most stuff in this file has moved to the formatters.h file above. The new functions are to avoid bringing ush into formatters.h - There are only two overloads because most string-based converters forward to the LPCWSTR overload.

[Holt59]

Changes here are mostly to change the message formatting when logging parameters.

[Holt59]

This is pure formatting and replacing typedef with using.

[Holt59]

This updates the shm_sink for spdlog - I moved the sink to the usvfs namespace because it took me some times to see that it was not a spdlog built-in sink.

[Holt59]

Remove unused function. Use spdlog built-in null sink. Updates for new spdlog.

[Holt59]

u8string -> string
test namespace

[Holt59]

u8string -> string
test namespace

[Holt59]

NtWriteFile takes a char*, not a const char*, so C++20 is not happy here

[Holt59]

u8string -> string