renderer: various fixes towards improving gpu calls robustness (#9188)

ensure framebuffer textures are detached and deleted, avoid leaving framebuffers bound when not needed

* render: avoid calling glDeleteProgram on no program

its safe to do so but it adds a bunch of unnecessery lines in apitrace
when tracing. if guard it and return early.

* opengl: ensure texture and buffers are unbound

ensure bound buffers are unbound after use, also detach textures from
framebuffer before deleting it otherwise it will become dangling and
essentially leak.

src/protocols/ToplevelExport.cpp

@@ -319,6 +319,12 @@ bool CToplevelExportFrame::copyShm(timespec* now) {
         g_pPointerManager->damageCursor(PMONITOR->self.lock());
     }
 
+    outFB.unbind();
+
+#ifndef GLES2
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
+#endif
+
     return true;
 }