fix: compilation errors with cpp_std=c++20

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.

src/modules/wlr/workspace_manager.cpp

@@ -379,7 +379,7 @@ Workspace::~Workspace() {
 }
 
 auto Workspace::update() -> void {
-  label_.set_markup(fmt::format(format_, fmt::arg("name", name_),
+  label_.set_markup(fmt::format(fmt::runtime(format_), fmt::arg("name", name_),
                                 fmt::arg("icon", with_icon_ ? get_icon() : "")));
 }