[client] egl: add cached uniforms and multipass effects

Replace the per-frame uniform list with stable, name-cached handles that
retain their values across shader recompilation. Track dirty uniforms so
only changed values are uploaded, reducing redundant GL calls and buffer
management.

Add a reusable effect-pass pipeline with per-pass shaders, samplers,
formats, resolutions, and intermediate render targets. This makes
external effects easier to integrate and supports arbitrary multipass
chains.

Migrate the desktop, cursor, damage, 24-bit, downscale, CAS, and FSR
rendering paths to the new APIs. Also ensure framebuffer objects are
released correctly.

client/renderers/EGL/framebuffer.c

@@ -57,7 +57,11 @@ void egl_framebufferFree(EGL_Framebuffer ** fb)
 {
   EGL_Framebuffer * this = *fb;
 
+  if (!this)
+    return;
+
   egl_textureFree(&this->tex);
+  glDeleteFramebuffers(1, &this->fbo);
   free(this);
   *fb = NULL;
 }