Never expand specialized columns that only contain wild patterns in them

Doing so would incur deeply nested expansion of the tree with no useful
side effects. This is problematic for "wide" data types such as structs
with dozens of fields but where only a few are actually being matched or bound.
Most notably, matching a fixed slice would use a number of stack frames that
grows with the number of elements in the slice.

Fixes #17877.
auto merge of #17944 : jakub-/rust/issue-17877, r=alexcrichton

Fixes #17877.