fix include/namespace related compilation errors (#7019)

a user on discord reported compilation errors when trying to compile
on Linux with GCC 13 and Clang 16.

src/tests/audio_core/hle/adts_reader.cpp

@@ -3,6 +3,8 @@
 // Refer to the license.txt file included.
 
 #include <catch2/catch_test_macros.hpp>
+#include <fmt/format.h>
+
 #include "audio_core/hle/adts.h"
 
 namespace {

src/tests/audio_core/hle/hle.cpp

@@ -3,6 +3,8 @@
 // Refer to the license.txt file included.
 
 #include <catch2/catch_test_macros.hpp>
+#include <fmt/core.h>
+
 #include "audio_core/hle/decoder.h"
 #include "audio_core/hle/hle.h"
 #include "audio_core/lle/lle.h"

src/tests/audio_core/lle/lle.cpp

@@ -3,6 +3,8 @@
 // Refer to the license.txt file included.
 
 #include <catch2/catch_test_macros.hpp>
+#include <fmt/core.h>
+
 #include "audio_core/hle/decoder.h"
 #include "audio_core/lle/lle.h"
 #include "common/common_paths.h"