Add a test that verifies that grab_window() returns something #15607

Job	Run time
android	1m 57s
build_and_test (ubuntu-22.04, stable)	6m 10s
cpp_test_driver (ubuntu-22.04)	6m 39s
cpp_cmake (ubuntu-22.04)	6m 57s
build_and_test (ubuntu-22.04, 1.73)	6m 11s
cpp_cmake (macos-12)	10m 41s
cpp_test_driver (macos-12)	4m 43s
build_and_test (macos-12, stable)	6m 11s
esp-idf-quick	9m 5s
cpp_cmake (windows-2022)	8m 37s
cpp_test_driver (windows-2022)	8m 27s
build_and_test (windows-2022, stable)	6m 5s
build_and_test (windows-2022, 1.73)	5m 51s
ffi_32bit_build	1m 7s
build_and_test (windows-2022, beta, --exclude ffmpeg --exclude gstreamer-player)	6m 7s
fmt_test	1m 42s
mcu (pico-st7789, thumbv6m-none-eabi)	39s
mcu (stm32h735g, thumbv7em-none-eabihf)	36s
miri	43s
mcu_esp	2m 25s
node_test (ubuntu-22.04)	3m 25s
node_test (macos-12)	15m 2s
python_test (ubuntu-22.04)	2m 12s
uefi-demo	36s
node_test (windows-2022)	15m 15s
updater_test (0.3.0)	1m 57s
python_test (macos-12)	1m 46s
python_test (windows-2022)	3m 38s
docs / docs	7m 5s
tree-sitter / tree-sitter-tests	9s
wasm / wasm	4m 33s
wasm_demo / wasm_demo	17m 52s
wasm / lint-slintpad	58s
wasm / build-slintpad	49s
cpp_package_test	2m 28s
	2h 58m 38s

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