Fix load subtask not being registered leading to false progress values. #27572

Job	Run time
📊 Static checks / Code style, file formatting, and docs	3m 19s
🤖 Android / Template (target=template_release)	3m 54s
🐧 Linux / Editor w/ Mono (target=editor)	4m 42s
🐧 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)	15m 28s
🍏 iOS / Template (target=template_release)	2m 11s
🍎 macOS / Editor (target=editor, tests=yes)	7m 1s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	6m 35s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	4m 33s
🍎 macOS / Template (target=template_release)	3m 16s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	6m 38s
🌐 Web / Template w/o threads (target=template_release, threads=no)	4m 19s
🐧 Linux / Template w/ Mono (target=template_release)	1m 41s
🏁 Windows / Editor (target=editor, tests=yes)	8m 59s
🐧 Linux / Minimal template (target=template_release, everything disabled)	1m 13s
🏁 Windows / Template (target=template_release)	7m 55s
🪲 Godot CPP / Build and test Godot CPP	7m 5s
	1h 28m 49s

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