Introduce MultimethodLoraConfig #7561

Job	Run time
test-executorch-metal-build / macos-job	6m 7s
test-metal-backend-modules / macos-job	9m 11s
export-model-metal-artifact (openai, whisper-large-v3-turbo, non-quantized) / macos-job	9m 26s
export-model-metal-artifact (mistralai, Voxtral-Mini-3B-2507, non-quantized) / macos-job	15m 31s
export-model-metal-artifact (nvidia, parakeet-tdt, non-quantized) / macos-job	10m 14s
export-model-metal-artifact (openai, whisper-small, non-quantized) / macos-job	8m 9s
export-model-metal-artifact (nvidia, parakeet-tdt, quantized-int4-metal) / macos-job	10m 26s
test-model-metal-e2e (mistralai, Voxtral-Mini-3B-2507, non-quantized) / macos-job	7m 18s
test-model-metal-e2e (openai, whisper-large-v3-turbo, non-quantized) / macos-job	5m 52s
test-model-metal-e2e (nvidia, parakeet-tdt, non-quantized) / macos-job	4m 54s
test-model-metal-e2e (openai, whisper-small, non-quantized) / macos-job	5m 32s
test-model-metal-e2e (nvidia, parakeet-tdt, quantized-int4-metal) / macos-job	4m 48s
	1h 37m 28s

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