Refactor editor theme generation and add spacing presets #19814

Job	Run time
📊 Static checks / Code style, file formatting, and docs	2m 50s
🤖 Android / Template (target=template_release)	4m 26s
🍏 iOS / Template (target=template_release)	2m 51s
🍎 macOS / Editor (target=editor, tests=yes)	13m 9s
🐧 Linux / Editor w/ Mono (target=editor)	10m 45s
🍎 macOS / Template (target=template_release)	5m 47s
🐧 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)	20m 57s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	11m 18s
🌐 Web / Template (target=template_release)	1m 47s
🏁 Windows / Editor (target=editor, tests=yes)	13m 37s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	10m 17s
🐧 Linux / Template w/ Mono (target=template_release)	2m 35s
🏁 Windows / Template (target=template_release)	6m 33s
🐧 Linux / Minimal template (target=template_release, everything disabled)	1m 47s
🪲 Godot CPP / Build and test Godot CPP	6m 52s
	1h 55m 31s

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