To keep the test filenames consistent, this patch:
* removes "test-" from file names (there used to be a mix of
"test-feature-1.mlir" and "feature-2.mlir"),
* replaces "_" with "-" (there used to be a mix of "feature-3.mlir"
and "feature_4.mlir").
Only files under test/Integration/Dialect/Vector/CPU are updated.