Fix LOD selection in compatibility backend and clean up LOD code #30881

Job	Run time
📊 Static checks / Code style, file formatting, and docs	31s
🤖 Android / Template (target=template_release)	30m 30s
🐧 Linux / Editor w/ Mono (target=editor)	41m 10s
🍎 macOS / Editor (target=editor, tests=yes)	31m 55s
🐧 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)	13m 38s
🍎 macOS / Template (target=template_release)	20m 8s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	34m 29s
🍏 iOS / Template (target=template_release)	1m 46s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	31m 27s
🐧 Linux / Template w/ Mono (target=template_release)	2m 2s
🐧 Linux / Minimal template (target=template_release, everything disabled)	2m 25s
🏁 Windows / Editor (target=editor, tests=yes)	48m 24s
🏁 Windows / Template (target=template_release)	32m 53s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	3m 54s
🌐 Web / Template w/o threads (target=template_release, threads=no)	3m 52s
🪲 Godot CPP / Build and test Godot CPP	7m 10s
	5h 6m 14s

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