[core] Keep BackendScope and context valid when closing the thread pool (#4307)

src/mbgl/vulkan/context.cpp

@@ -68,8 +68,6 @@ Context::Context(RendererBackend& backend_)
 Context::~Context() noexcept {
     MBGL_VERIFY_THREAD(tid);
 
-    backend.getThreadPool().runRenderJobs(true /* closeQueue */);
-
     destroyResources();
 
     {

src/mbgl/vulkan/renderer_backend.cpp

@@ -634,6 +634,9 @@ void RendererBackend::initCommandPool() {
 void RendererBackend::destroyResources() {
     if (device) device->waitIdle(dispatcher);
 
+    gfx::BackendScope scope(*this, gfx::BackendScope::ScopeType::Implicit);
+    getThreadPool().runRenderJobs(true /* closeQueue */);
+
     context.reset();
     commandPool.reset();