Fix use-after-free of `ConditionVariable` in `ResourceLoader` #35806

Job	Run time
📊 Static checks / Code style, file formatting, and docs	24s
🤖 Android / Editor (target=editor)	18m 21s
🤖 Android / Template arm32 (target=template_release, arch=arm32)	4m 45s
🤖 Android / Template arm64 (target=template_release, arch=arm64)	4m 34s
🍏 iOS / Template (target=template_release)	6m 45s
🍎 macOS / Editor (target=editor, tests=yes)	25m 44s
🍎 macOS / Template (target=template_release)	14m 2s
🐧 Linux / Editor w/ Mono (target=editor)	40m 7s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	18m 1s
🐧 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)	46m 53s
🌐 Web / Template w/o threads (target=template_release, threads=no)	19m 5s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	36m 1s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	24m 51s
🏁 Windows / Editor (target=editor, tests=yes)	48m 28s
🐧 Linux / Template w/ Mono (target=template_release)	26m 31s
🏁 Windows / Template (target=template_release)	33m 51s
🐧 Linux / Minimal template (target=template_release, everything disabled)	5m 19s
🪲 Godot CPP / Build and test Godot CPP	8m 23s
	6h 22m 5s

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