Vectorizing a rank-0 `linalg.generic` whose body contains
`tensor.extract` with data-dependent indices hits the Gather
classification in `getTensorExtractMemoryAccessPattern` because
`isOutput1DVector` returns false for a 0-D result. This produces an
invalid `vector.gather` where operand #2 must be a vector of index
values but gets a scalar `index` instead.
Fix classifies a 0-D result as ScalarBroadcast rather than Gather, and
skips mask generation for 0-D in that path.
ae6fbd0fb7