Add Perf Kernels

This is a combination of 2 commits.

Add Perf Kernels

Add Perf Kernels

This is a combination of 6 commits.

add perf-kernels

fix formating issues

fix unused variables and other bugs

fix other issues

remove scripts

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format

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Change all block pointers to tensor pointers

Block pointers are for nvidia TMAs. They are useful for regular loads as well but not well supported.

Also cleaned up some code I came across along the way and updated comment at the top.

Add support for layouts commonly used by users.

Add option for varlen / thd layout to specify equal context lengths for all batches. Also often used by users.

Set SM scale multiplication to a constexpr. Minor asm improvement.

Changed acc scaling to adjust for softmax division to
multiplication with reciprocal. ~10% perf improvement.