Implement Pdist Backward

[anhskrttt]

• Add Pdist operation with backward kernels.
• Add driver and gtest for kernels.

Average improvement over ROCm

type	bwd
float	1.65
float16	-
bfloat16	-

• ROCm pytorch doesn't support for float16 and bfloat16 , so these are always winning cases.

Detail Benchmark

fp32

dtype	size	is_contiguous	ROCm	MIOpen	Improvement
float32	[2 5]	noncontiguous	191678	33119	5.787554
float32	[16 255]	noncontiguous	178239	32266	5.524050
float32	[25 100]	noncontiguous	157438	33741	4.666074
float32	[5 10]	contiguous	104480	22577	4.627718
float32	[25 300]	noncontiguous	151519	33333	4.545615
float32	[2000 3000]	contiguous	291086060	92748000	3.138462
float32	[10 65536]	noncontiguous	328958	109723	2.998077
float32	[100 10]	noncontiguous	123679	45119	2.741173
float32	[100 20]	contiguous	96960	43039	2.252840
float32	[800 2329]	contiguous	43446243	19770900	2.197484
float32	[800 498]	contiguous	8592417	3999580	2.148330
float32	[1044 80]	contiguous	1641588	1301320	1.261479
float32	[5199 80]	contiguous	37923721	30627700	1.238216
float32	[4918 80]	contiguous	33406313	29107700	1.147680
float32	[4558 80]	contiguous	28701388	25077400	1.144512
float32	[993 80]	noncontiguous	1499829	1326410	1.130743
float32	[2048 512]	noncontiguous	83486114	74272700	1.124048
float32	[128 128]	noncontiguous	134079	120408	1.113539
float32	[237 80]	contiguous	164639	148390	1.109502
float32	[4061 80]	noncontiguous	22037119	20823500	1.058281
float32	[258 80]	contiguous	172159	162719	1.058014
float32	[4077 80]	noncontiguous	22334398	21159900	1.055506
float32	[4050 80]	noncontiguous	21789601	20755800	1.049808
float32	[4508 80]	noncontiguous	28472270	27136500	1.049224
float32	[285 80]	contiguous	186239	184105	1.011591