ImGui: Remove close button from debug windows

They can be closed by unchecking the setting instead, and it stays in
sync with the config this way.

src/core/cdrom.cpp

@@ -2322,7 +2322,7 @@ void CDROM::DrawDebugWindow()
   const float framebuffer_scale = ImGui::GetIO().DisplayFramebufferScale.x;
 
   ImGui::SetNextWindowSize(ImVec2(800.0f * framebuffer_scale, 550.0f * framebuffer_scale), ImGuiCond_FirstUseEver);
-  if (!ImGui::Begin("CDROM State", &g_settings.debugging.show_cdrom_state))
+  if (!ImGui::Begin("CDROM State", nullptr))
   {
     ImGui::End();
     return;

src/core/dma.cpp

@@ -625,7 +625,7 @@ void DMA::DrawDebugStateWindow()
   const float framebuffer_scale = ImGui::GetIO().DisplayFramebufferScale.x;
 
   ImGui::SetNextWindowSize(ImVec2(850.0f * framebuffer_scale, 250.0f * framebuffer_scale), ImGuiCond_FirstUseEver);
-  if (!ImGui::Begin("DMA State", &g_settings.debugging.show_dma_state))
+  if (!ImGui::Begin("DMA State", nullptr))
   {
     ImGui::End();
     return;

src/core/gpu.cpp

@@ -1525,7 +1525,7 @@ void GPU::DrawDebugStateWindow()
   const float framebuffer_scale = ImGui::GetIO().DisplayFramebufferScale.x;
 
   ImGui::SetNextWindowSize(ImVec2(450.0f * framebuffer_scale, 550.0f * framebuffer_scale), ImGuiCond_FirstUseEver);
-  if (!ImGui::Begin("GPU", &g_settings.debugging.show_gpu_state))
+  if (!ImGui::Begin("GPU", nullptr))
   {
     ImGui::End();
     return;

src/core/mdec.cpp

@@ -726,7 +726,7 @@ void MDEC::DrawDebugStateWindow()
   const float framebuffer_scale = ImGui::GetIO().DisplayFramebufferScale.x;
 
   ImGui::SetNextWindowSize(ImVec2(300.0f * framebuffer_scale, 350.0f * framebuffer_scale), ImGuiCond_FirstUseEver);
-  if (!ImGui::Begin("MDEC State", &g_settings.debugging.show_mdec_state))
+  if (!ImGui::Begin("MDEC State", nullptr))
   {
     ImGui::End();
     return;

src/core/spu.cpp

@@ -1874,7 +1874,7 @@ void SPU::DrawDebugStateWindow()
   const float framebuffer_scale = ImGui::GetIO().DisplayFramebufferScale.x;
 
   ImGui::SetNextWindowSize(ImVec2(800.0f * framebuffer_scale, 800.0f * framebuffer_scale), ImGuiCond_FirstUseEver);
-  if (!ImGui::Begin("SPU State", &g_settings.debugging.show_spu_state))
+  if (!ImGui::Begin("SPU State", nullptr))
   {
     ImGui::End();
     return;

src/core/timers.cpp

@@ -408,7 +408,7 @@ void Timers::DrawDebugStateWindow()
   const float framebuffer_scale = ImGui::GetIO().DisplayFramebufferScale.x;
 
   ImGui::SetNextWindowSize(ImVec2(800.0f * framebuffer_scale, 100.0f * framebuffer_scale), ImGuiCond_FirstUseEver);
-  if (!ImGui::Begin("Timer State", &g_settings.debugging.show_timers_state))
+  if (!ImGui::Begin("Timer State", nullptr))
   {
     ImGui::End();
     return;