[client] egl: switch to using GL_TEXTURE_EXTERNAL_OES for DMABUF

According to Erik @ NVidia the open source NVidia driver will not
create a EGLImage from a DMABUF if the target is not
GL_TEXTURE_EXTERNAL_OES. This change set converts the dmabuf texture
from GL_TEXTURE_2D to GL_TEXTURE_EXTERNAL_OES and at runtime performs a
global search & replace on fragment shaders as needed to remain
compatible, replacing `sampler2D` with `samplerExternalOES`.

Ref: https://github.com/NVIDIA/open-gpu-kernel-modules/discussions/243#discussioncomment-3283415

client/renderers/EGL/texture_framebuffer.c

@@ -147,5 +147,6 @@ EGL_TextureOps EGL_TextureFrameBuffer =
   .setup   = egl_texFBSetup,
   .update  = egl_texFBUpdate,
   .process = egl_texBufferStreamProcess,
-  .get     = egl_texBufferStreamGet
+  .get     = egl_texBufferStreamGet,
+  .bind    = egl_texBufferBind
 };