Add missing descriptions to remaining signals. #443

Job	Run time
📊 Static checks / Code style, file formatting, and docs	2m 51s
🍏 iOS / Template (target=template_release)	3m 18s
🤖 Android / Template (target=template_release)	3m 26s
🍎 macOS / Editor (target=editor, tests=yes)	1m 30s
🐧 Linux / Editor w/ Mono (target=editor)	3m 51s
🍎 macOS / Template (target=template_release)	1m 41s
🐧 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)	11m 47s
🌐 Web / Template (target=template_release)	1m 6s
🏁 Windows / Editor (target=editor, tests=yes)	7m 6s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	5m 5s
🏁 Windows / Template (target=template_release)	6m 26s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	6m 23s
🐧 Linux / Template w/ Mono (target=template_release)	59s
🐧 Linux / Minimal template (target=template_release, everything disabled)	43s
🪲 Godot CPP / Build and test Godot CPP	6m 44s
	1h 2m 56s

Provide feedback