Replaces std::wstring_convert etc with uftcpp library, since these will be removed by C++26

What's Changed

• Updated fmt to 12.0.0 by @5cript in #139

fmtlib/fmt#4543

Full Changelog: v1.0.2...v1.0.3

Fixed build with boost version 1.8.9

CMake 4.0 deprecates CMake version 3.5 or lower.
2 Dependencies had this problem portable-file-dialogs and libcpppre.
The former was allowed to continue to build, libcpppre has been replaced with another library living in the NuiCpp Organization.
libcpppre was only used for effectively 1 line of code.
The makeshift function traits impl in Nui has also been removed by the tested, more encompassing alternative.

This also includes a small build time optimization that makes it so that the emscripten target is not configured on every build, when it was configured already. The CONFIGURE_ALWAYS flag as a fallback to get the old behavior in case something unforseen happens by this change / some inproper CMake is used in the frontend/emscripten target.

Updated emscripten to 4.0.4, removed some no longer necessary fixup tools running on windows, because it now works out of the box.
Dropped support for Ubuntu 20

libc++ reduced transitive includes in C++23.
Added missing header.

Update underlying dependencies to work with newer boost versions.

What's Changed

• Clang Tidy Improvements & OBSERVED_BUNDLE_FILES by @5cript in #127
• Fixed scope exit class. by @5cript, reported by @DNKpp in #128

Full Changelog: v0.18.1...v0.18.2