[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/MG_Util/Debug/Log.cpp

@@ -63,6 +63,8 @@ namespace MobileGL {
         void InitFile() {
 #if MOBILEGL_LOG_ENABLE_FILE
             if (!s_logFile) {
+                // MOBILEGL_LOG_FILE_PATH must stay a raw getenv (not MG_Config::Features):
+                // InitFile() runs before MG_ConfigLoader::Init() in MobileGL::Initialize().
                 const char* logPath = std::getenv("MOBILEGL_LOG_FILE_PATH");
                 if (!logPath || !*logPath) {
                     logPath = MOBILEGL_LOG_FILE_PATH;