QMoE: fail loudly when weights_prepacked=0 but PrePack did not run #15747

Job	Run time
precheck	1m 39s
wasm_Release / build-wasm	41m 38s
wasm_Debug / build-wasm	38m 53s
wasm_Release_static_library / build-wasm	6m 19s
web_Debug / build_onnxruntime_web	20m 32s
web_Release / build_onnxruntime_web	23m 46s
	2h 12m 47s

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