[GDScript] Correctly report invalid read-only access #29126

Job	Run time
📊 Static checks / Code style, file formatting, and docs	3m 19s
🍎 macOS / Editor (target=editor, tests=yes)	24m 33s
🍎 macOS / Template (target=template_release)	14m 24s
🐧 Linux / Editor w/ Mono (target=editor)	35m 23s
🐧 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)	40m 15s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	29m 50s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	27m 40s
🤖 Android / Template (target=template_release)	25m 8s
🐧 Linux / Template w/ Mono (target=template_release)	20m 14s
🍏 iOS / Template (target=template_release)	8m 3s
🐧 Linux / Minimal template (target=template_release, everything disabled)	13m 51s
🏁 Windows / Editor (target=editor, tests=yes)	43m 4s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	19m 39s
🏁 Windows / Template (target=template_release)	29m 26s
🌐 Web / Template w/o threads (target=template_release, threads=no)	19m 20s
🪲 Godot CPP / Build and test Godot CPP	7m 5s
	6h 1m 14s

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