GPU: Add a simplified OpenGL ES renderer

Seems this is the only way to get semi-decent performance out of Mali
drivers :/

src/core/gpu_hw_opengl_es.h

@@ -0,0 +1,69 @@
+#pragma once
+#include "common/gl/program.h"
+#include "common/gl/stream_buffer.h"
+#include "common/gl/texture.h"
+#include "glad.h"
+#include "gpu_hw.h"
+#include <array>
+#include <memory>
+#include <tuple>
+
+class GPU_HW_OpenGL_ES : public GPU_HW
+{
+public:
+  GPU_HW_OpenGL_ES();
+  ~GPU_HW_OpenGL_ES() override;
+
+  bool Initialize(HostDisplay* host_display, System* system, DMA* dma, InterruptController* interrupt_controller,
+                  Timers* timers) override;
+  void Reset() override;
+
+  void ResetGraphicsAPIState() override;
+  void RestoreGraphicsAPIState() override;
+  void UpdateSettings() override;
+
+protected:
+  void UpdateDisplay() override;
+  void ReadVRAM(u32 x, u32 y, u32 width, u32 height) override;
+  void FillVRAM(u32 x, u32 y, u32 width, u32 height, u32 color) override;
+  void UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void* data) override;
+  void CopyVRAM(u32 src_x, u32 src_y, u32 dst_x, u32 dst_y, u32 width, u32 height) override;
+  void FlushRender() override;
+  void MapBatchVertexPointer(u32 required_vertices) override;
+  void UpdateVRAMReadTexture() override;
+
+private:
+  struct GLStats
+  {
+    u32 num_batches;
+    u32 num_vertices;
+    u32 num_vram_reads;
+    u32 num_vram_writes;
+    u32 num_vram_read_texture_updates;
+    u32 num_uniform_buffer_updates;
+  };
+
+  std::tuple<s32, s32> ConvertToFramebufferCoordinates(s32 x, s32 y);
+
+  void SetCapabilities(HostDisplay* host_display);
+  void CreateFramebuffer();
+  void ClearFramebuffer();
+  void DestroyFramebuffer();
+
+  bool CompilePrograms();
+  void SetVertexPointers();
+  void SetDrawState(BatchRenderMode render_mode);
+  void SetScissorFromDrawingArea();
+
+  // downsample texture - used for readbacks at >1xIR.
+  std::unique_ptr<GL::Texture> m_vram_texture;
+  std::unique_ptr<GL::Texture> m_vram_read_texture;
+  std::unique_ptr<GL::Texture> m_vram_encoding_texture;
+  std::unique_ptr<GL::Texture> m_display_texture;
+
+  std::vector<BatchVertex> m_vertex_buffer;
+
+  std::array<std::array<std::array<GL::Program, 2>, 9>, 4> m_render_programs; // [render_mode][texture_mode][dithering]
+  std::array<std::array<GL::Program, 2>, 2> m_display_programs;               // [depth_24][interlaced]
+  GL::Program m_vram_read_program;
+};