add fmt:: namespace to distinguish from std::format_to (#43)

When compiled with new toolchain that implements std::format_to, it become
ambiguous on which one should be called. Due to argument-dependent lookup, even
if we are not `using namespace std;` the std version is still considered. So
let's add fmt:: to avoid ambiguous compilation error.

src/meta/components/SessionManager.h

@@ -134,11 +134,11 @@ template <>
 struct formatter<hf3fs::meta::server::FileSession> : formatter<std::string_view> {
   template <typename FormatContext>
   auto format(const hf3fs::meta::server::FileSession &session, FormatContext &ctx) const {
-    return format_to(ctx.out(),
-                     "{{inodeId {}, client {}, session {}}}",
-                     session.inodeId,
-                     session.clientId,
-                     session.sessionId);
+    return fmt::format_to(ctx.out(),
+                          "{{inodeId {}, client {}, session {}}}",
+                          session.inodeId,
+                          session.clientId,
+                          session.sessionId);
   }
 };