Overhaul CanvasItem documentation #619

Job	Run time
📊 Static checks / Code style, file formatting, and docs	28s
🍏 iOS / Template (target=template_release)	2m 30s
🐧 Linux / Editor w/ Mono (target=editor)	5m 29s
🐧 Linux / Editor with doubles and GCC sanitizers (target=editor, tests=yes, dev_build=yes, scu_build=yes, precision=double, use_asan=yes, use_ubsan=yes, linker=gold)	40m 26s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	6m 32s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	8m 5s
🐧 Linux / Template w/ Mono (target=template_release)	59s
🍎 macOS / Editor (target=editor, tests=yes)	3m 22s
🤖 Android / Editor (target=editor)	3m 34s
🐧 Linux / Minimal template (target=template_release, everything disabled)	1m 34s
🍎 macOS / Template (target=template_release)	2m 47s
🤖 Android / Template arm32 (target=template_release, arch=arm32)	3m 0s
🤖 Android / Template arm64 (target=template_release, arch=arm64)	3m 12s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	3m 55s
🌐 Web / Template w/o threads (target=template_release, threads=no)	3m 47s
🏁 Windows / Editor (target=editor, tests=yes)	9m 11s
🏁 Windows / Template (target=template_release)	8m 20s
🪲 Godot CPP	0s
	1h 47m 11s

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