Dear ImGui Implementation (#598)

* added imgui as dependency

* imgui renderer/basic input implementation

* imgui: add layers system

Add video info layer to show fps. Press F10 to toggle it.

* imgui: add custom imgui config

* imgui: gamepad capture, stopping propagation

* imgui: changed config & log file path to use portable dir

* videoout: render blank frame when video output is closed

required to render imgui even when game has no video output

- fixed merge compile-error

src/common/logging/filter.cpp

@@ -117,6 +117,7 @@ bool ParseFilterRule(Filter& instance, Iterator begin, Iterator end) {
     CLS(Render)                                                                                    \
     SUB(Render, Vulkan)                                                                            \
     SUB(Render, Recompiler)                                                                        \
+    CLS(ImGui)                                                                                     \
     CLS(Input)                                                                                     \
     CLS(Tty)                                                                                       \
     CLS(Loader)

src/common/logging/types.h

@@ -84,6 +84,7 @@ enum class Class : u8 {
     Render,             ///< Video Core
     Render_Vulkan,      ///< Vulkan backend
     Render_Recompiler,  ///< Shader recompiler
+    ImGui,              ///< ImGui
     Loader,             ///< ROM loader
     Input,              ///< Input emulation
     Tty,                ///< Debug output from emu