settings: Enable FIFO relaxed

Not entirely sure if we need this, but there's also no reason not to
support it.

settings: Give VSyncMode values

src/common/settings.h

@@ -17,9 +17,10 @@
 namespace Settings {
 
 enum class VSyncMode : u32 {
-    Immediate,
-    FIFO,
-    Mailbox,
+    Immediate = 0,
+    Mailbox = 1,
+    FIFO = 2,
+    FIFORelaxed = 3,
 };
 
 enum class RendererBackend : u32 {
@@ -461,8 +462,8 @@ struct Values {
     SwitchableSetting<NvdecEmulation> nvdec_emulation{NvdecEmulation::GPU, "nvdec_emulation"};
     SwitchableSetting<bool> accelerate_astc{true, "accelerate_astc"};
     SwitchableSetting<bool> async_astc{false, "async_astc"};
-    Setting<VSyncMode, true> vsync_mode{VSyncMode::FIFO, VSyncMode::Immediate, VSyncMode::Mailbox,
-                                        "use_vsync"};
+    Setting<VSyncMode, true> vsync_mode{VSyncMode::FIFO, VSyncMode::Immediate,
+                                        VSyncMode::FIFORelaxed, "use_vsync"};
     SwitchableSetting<ShaderBackend, true> shader_backend{ShaderBackend::GLSL, ShaderBackend::GLSL,
                                                           ShaderBackend::SPIRV, "shader_backend"};
     SwitchableSetting<bool> use_asynchronous_shaders{false, "use_asynchronous_shaders"};

src/core/telemetry_session.cpp

@@ -89,10 +89,12 @@ static constexpr const char* TranslateVSyncMode(Settings::VSyncMode mode) {
     switch (mode) {
     case Settings::VSyncMode::Immediate:
         return "Immediate";
-    case Settings::VSyncMode::FIFO:
-        return "FIFO";
     case Settings::VSyncMode::Mailbox:
         return "Mailbox";
+    case Settings::VSyncMode::FIFO:
+        return "FIFO";
+    case Settings::VSyncMode::FIFORelaxed:
+        return "FIFO Relaxed";
     }
     return "Unknown";
 }