TST: parametrize CoW indexing tests for extension (nullable) dtypes (#51208)

Author: jorisvandenbossche

pandas/core/internals/managers.py

@@ -838,8 +838,9 @@ def _slice_take_blocks_ax0(
                     # A non-consolidatable block, it's easy, because there's
                     # only one item and each mgr loc is a copy of that single
                     # item.
+                    deep = not (only_slice or using_copy_on_write())
                     for mgr_loc in mgr_locs:
-                        newblk = blk.copy(deep=not only_slice)
+                        newblk = blk.copy(deep=deep)
                         newblk.mgr_locs = BlockPlacement(slice(mgr_loc, mgr_loc + 1))
                         blocks.append(newblk)