recognize and issue error if GPU does not support bf16 #3281

Job	Run time
gather-models-cpu	12s
gather-models-gpu	11s
test-gguf-util (macos-14)	4m 9s
test-mps (macos-m1-stable)	1m 25s
test-mps-dtype (macos-m1-stable)	1m 55s
test-tinystories-executorch (16-core-ubuntu)	18m 40s
test-tinystories-executorch (macos-14-xlarge)	16m 2s
torchchat-command-load-test (macos-14)	1m 43s
compile-gguf (macos-14)	6m 1s
runner-aoti (16-core-ubuntu)	6m 6s
runner-et (16-core-ubuntu)	7m 11s
runner-et (macos-14-xlarge)	7m 50s
test-torchao-experimental (macos-14-xlarge)	12m 39s
runner-aoti (macos-14-xlarge)	3m 18s
test-build-runner-et-android / linux-job	12m 2s
test-gpu-aoti-float16 (cuda, stories15M) / linux-job	13m 12s
test-gpu-aoti-float32 (cuda, stories15M) / linux-job	13m 22s
test-gpu-compile (cuda, stories15M) / linux-job	13m 11s
test-gpu-aoti-bfloat16 (cuda, stories15M) / linux-job	8m 10s
test-gpu-eval-sanity-check (cuda, stories15M) / linux-job	8m 3s
test-cpu-eval-sanity-check (x86_64, stories15M)	10m 29s
test-cpu-aoti (x86_64, stories15M)	17m 41s
test-cpu-eval-sanity-check (aarch64, stories15M)	10m 40s
test-cpu-compile (x86_64, stories15M)	16m 43s
test-cpu-aoti (aarch64, stories15M)	9m 30s
test-cpu-compile (aarch64, stories15M)	9m 38s
test-cpu-eval-sanity-check-float32 (x86_64, stories15M)	38m 22s
test-cpu-eval-sanity-check-float16 (x86_64, stories15M)	30m 31s
test-cpu-eval-sanity-check-float32 (aarch64, stories15M)	9m 3s
test-cpu-eval-sanity-check-float16 (aarch64, stories15M)	10m 9s
	5h 18m 8s

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