Revert "Initial private SDP interface and naive composite impl (#81956)"
This reverts commit f15c5bf13387bde01af48f27d44ad853c004308d.
Reverted https://github.com/pytorch/pytorch/pull/81956 on behalf of https://github.com/janeyx99 due to broke all configs on test_scaled_dot_product_attention (__main__.TestNestedTensorAutograd) https://hud.pytorch.org/pytorch/pytorch/commit/f15c5bf13387bde01af48f27d44ad853c004308d
