Remove `LayoutSpec` and undeprecate `StyleMetrics.layout-*` properties #18837

Job	Run time
python_test (ubuntu-22.04)	2m 8s
cpp_test_driver (ubuntu-22.04)	6m 59s
build_and_test (ubuntu-22.04, 1.77)	14m 18s
python_test (macos-14)	1m 45s
cpp_test_driver (macos-13)	11m 32s
python_test (windows-2022)	2m 49s
build_and_test (macos-14, stable)	19m 30s
cpp_cmake (macos-14, 1.77)	7m 43s
cpp_test_driver (windows-2022)	9m 21s
build_and_test (windows-2022, stable)	23m 5s
cpp_cmake (windows-2022, nightly)	10m 3s
cpp_cmake (ubuntu-22.04, stable)	7m 16s
build_and_test (windows-2022, 1.77)	22m 59s
mcu (pico-st7789, thumbv6m-none-eabi)	30s
mcu_esp	2m 46s
mcu (pico2-st7789, thumbv8m.main-none-eabihf)	35s
mcu (stm32h735g, thumbv7em-none-eabihf)	47s
node_test (ubuntu-22.04)	2m 58s
build_and_test (windows-2022, beta, --exclude ffmpeg --exclude gstreamer-player)	30m 14s
vsce_build_test	6m 25s
node_test (macos-14)	2m 8s
build_and_test (ubuntu-22.04, nightly)	16m 41s
node_test (windows-2022)	6m 9s
ffi_32bit_build	1m 14s
fmt_test	1m 39s
android	1m 57s
esp-idf-quick	9m 5s
updater_test (0.3.0)	1m 23s
miri	47s
docs / docs	4m 27s
tree-sitter / tree-sitter-tests	10s
wasm / wasm	4m 35s
wasm_demo / wasm_demo	2m 35s
format_lint_typecheck / format_lint_typecheck	2m 54s
cpp_package_test	2m 8s
wasm / build-slintpad	1m 35s
	4h 3m 10s

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