[Refactor] (MG_Config): centralize env-var and driver-feature reads

MG_Config::FeaturesTable snapshots every MOBILEGL_* toggle once in
ConfigLoader::Init with a single truthy rule (non-empty, not '0', not
'false' case-insensitively), replacing 13 scattered std::getenv sites
that used four different parsing conventions. Renderer-derived bits
(IsAngleRenderer/IsAngleLlvmpipeRenderer/AvoidSamplerMipmapMinFilter)
move into GLESCapabilities, set once in FillInGLESCapabilities, so hot
paths (glMemoryBarrier ANGLE flush, sampler min-filter sync) stop doing
per-call string scans. MOBILEGL_PRESENT_DUMP_CALL/_CURRENT_CALL stay
live getenv (the retrace harness mutates them at runtime) and
MOBILEGL_LOG_FILE_PATH stays in Log.cpp (log init precedes config
init); both are documented in Config.h. Known semantic unification:
MOBILEGL_DISABLE_SUBGROUP previously required exactly 'true' and
MOBILEGL_PRESENT_STATS exactly '1'; both now follow the shared rule
(CI's 0/1 values parse identically). Also bumps CoreVersion to 26.07.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

MobileGL/Init.cpp

@@ -13,7 +13,6 @@
 #include <MG_State/EGLState/Core.h>
 #include <MG_Impl/GLImpl/Texture/ProxyTexture.h>
 #include <MG_Impl/GLImpl/Framebuffer/GL_Framebuffer.h>
-#include <cstdlib>
 
 namespace MobileGL {
     namespace {
@@ -75,7 +74,7 @@ namespace MobileGL {
     }
 
     __attribute__((destructor)) static void AutoDestroy() {
-        if (std::getenv("MOBILEGL_TRACE_SKIP_AUTODESTROY") != nullptr) {
+        if (MG_Config::Features.TraceSkipAutodestroy) {
             return;
         }
 #if defined(__APPLE__)