[LLVMCPU][NFC] Separate the intrinsic MNK shape from its register layout (#24861)

`getIntrinsicMNKShape` states how many M/N/K elements one invocation of
an intrinsic computes, independent of how those elements are laid out in
registers. Selection scores candidates on this shape and the
sibling-pairing validator checks M and N against it, so every intrinsic
declares one, including scalable ones, which declare their base sizes. A
scalable and a non-scalable intrinsic should never compete for the same
matmul, so comparisons stay like-for-like.

The hand-rolled swizzles for intrinsics whose tiles are not row-major
move into `getNonRowMajorIntrinsicSwizzle`.

Assisted-by: Claude Code

Signed-off-by: Ege Beysel <beyselege@gmail.com>