[Example] Add TileKernels Examples in Tilus

[WilliamZhang20]

Kernel List:

• swiglu_forward_and_per_token_cast_kernel
• per_token_cast

Benchmarks on H200 NVL:

Per-token FP8 cast matches reference for size (257, 4096); max code diff=32; dequantized sum diff=1.21161
   tokens  hidden  tilekernels (ms)  tilus (ms) speedup  sum diff
0     128    1024          0.006592    0.005952   1.11x  0.079254
1     256    2048          0.007168    0.006336   1.13x  0.960876
2     257    4096          0.008096    0.007328   1.10x  1.211609

SwiGLU FP8 cast matches reference for size (1024, 4096); max code diff=2; dequantized sum diff=0.0253906
   tokens  hidden  tilekernels (ms)  tilus (ms) speedup  sum diff
0     128    1024          0.008768    0.006400   1.37x  0.000092
1     256    2048          0.008320    0.007264   1.15x  0.000061
2     257    4096          0.010688    0.008448   1.27x  0.000122
3    1024    4096          0.019648    0.014080   1.40x  0.025391

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[yaoyaoding]

Thanks @WilliamZhang20 , LGTM in general.

[yaoyaoding]

/ok to test e6c70ef

[yaoyaoding]

/ok to test 7638df8