Use Packed*Array over Vector<T> in Variant #476

Job	Run time
📊 Static checks / Code style, file formatting, and docs	2m 46s
🤖 Android / Template (target=template_release)	28m 36s
🐧 Linux / Editor w/ Mono (target=editor)	34m 32s
🍎 macOS / Editor (target=editor, tests=yes)	38m 2s
🍏 iOS / Template (target=template_release)	34m 17s
🐧 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)	35m 39s
🍎 macOS / Template (target=template_release)	16m 49s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	31m 54s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	20m 57s
🏁 Windows / Editor (target=editor, tests=yes)	49m 26s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	27m 46s
🌐 Web / Template w/o threads (target=template_release, threads=no)	21m 14s
🐧 Linux / Template w/ Mono (target=template_release)	22m 56s
🏁 Windows / Template (target=template_release)	33m 14s
🐧 Linux / Minimal template (target=template_release, everything disabled)	14m 16s
🪲 Godot CPP / Build and test Godot CPP	6m 45s
	6h 59m 9s

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