Add unit test runner for autocompletion #18945

Job	Run time
📊 Static checks / Code style, file formatting, and docs	29s
🤖 Android / Template (target=template_release)	4m 6s
🍎 macOS / Editor (target=editor, tests=yes)	7m 45s
🏁 Windows / Editor (target=editor, tests=yes)	9m 54s
🍎 macOS / Template (target=template_release)	4m 49s
🏁 Windows / Template (target=template_release)	7m 35s
🐧 Linux / Editor w/ Mono (target=editor)	5m 51s
🍏 iOS / Template (target=template_release)	3m 30s
🐧 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)	16m 58s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	6m 1s
🌐 Web / Template (target=template_release)	1m 39s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	6m 30s
🐧 Linux / Template w/ Mono (target=template_release)	2m 52s
🐧 Linux / Minimal template (target=template_release, everything disabled)	2m 3s
🪲 Godot CPP / Build and test Godot CPP	6m 45s
	1h 26m 47s

Provide feedback