[Perf] (MG_Backend/DirectGLES, MG_Impl): cache link-time lookups, bound unit scans, honor eglSwapInterval

- BackendProgramObjectImpl::CacheResourceLocations resolves every
  glGetUniformBlockIndex / glGetUniformLocation string query once per
  link and establishes the block binding points there. Per draw,
  BindCurrentProgramWithResources now uses the cached indices, re-issues
  glUniform1i only when a sampler's unit actually changed (program state
  persists), uploads the global UBO only when its content version moved,
  and skips redundant glUseProgram binds (guard reset on program-name
  reuse, MakeCurrent, and every explicit glUseProgram(0)). The caches are
  invalidated through ProgramObject's link version, which also makes a
  relinked program finally re-sync its backend program.
- Track a texture-unit high-water mark (fed by glBindTexture /
  glBindTextureUnit / glBindSampler / glBindImageTexture) so the two
  per-draw unit scans (MAX_TEXTURE_IMAGE_UNITS is 192) and the
  texture-deletion unbind loop only walk units that were ever touched.
- Forward the app's eglSwapInterval to the native EGL surface through a
  new BackendObject::SetEGLSwapInterval hook (applied immediately when
  the surface exists, otherwise deferred to surface creation /
  MakeCurrent). "VSync off" finally reaches the hardware - DirectGLES
  was hard-locked to the display refresh before.

The driver-side cost of the per-draw string lookups was about half of a
30% Adreno driver hotspot; libMobileGL's share of the vanilla render
thread fell from 22% to 9% (simpleperf, Adreno 830).

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

MobileGL/MG_Backend/DirectGLES/DirectGLES.h

@@ -110,6 +110,9 @@ namespace MobileGL::MG_Backend::DirectGLES {
     void DeleteSync(BackendSyncHandle sync);
     Bool GetSyncStatus(BackendSyncHandle sync);
     void Present();
+    // Applies (or defers until the window surface exists) the app-requested
+    // eglSwapInterval on the native EGL surface.
+    void SetSwapInterval(Int interval);
     void SetEGLFuncsTable(const MG_External::EGLFunctionsTable& eglFuncs);
     void SetGLESFuncsTable(const MG_External::GLESFunctionsTable& glesFuncs);
     void SetGLESCapabilities(const MG_External::GLESCapabilities& capabilities);