Add `setup_no_sqarray` builder method (#384)

* Add `setup_no_sqarray` builder method.

This exposes `IORING_SETUP_NO_SQARRAY` (available since Linux 6.6) which
removes the SQ index array indirection, eliminating a memory read per
submission.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix NO_SQARRAY ring header corruption.

When IORING_SETUP_NO_SQARRAY is set, the kernel sets sq_off.array to 0.
The SQ array initialization loop was writing to offset 0 of the SQ mmap,
corrupting the ring header (sq_head, sq_tail, etc.). Skip the array
initialization when NO_SQARRAY is set since the kernel consumes SQEs
directly by ring index.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Add test for setup_no_sqarray.

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>