Metal backend: Add gated delta rule kernel for linear attention #2979

Job	Run time
test-arm / test-backend-linux (arm_tosa_fp, models) / linux-job	30m 58s
test-arm / test-backend-linux (arm_vgf_fp, models) / linux-job	33m 56s
test-arm / test-backend-linux (arm_vgf_fp, operators) / linux-job	16m 50s
test-arm / test-backend-linux (arm_tosa_fp, operators) / linux-job	19m 36s
test-arm / test-backend-macos	-1s
test-arm / package-golden-artifacts	42s
	1h 42m 1s

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