Replace `type_is_pod` contents with `is_pod`

Instead of using the old implementation, make this function use `is_pod`
which is implemented in the `TypeContents` trait.

Note: `type_is_pod` is currently not being used anywhere. I kept it so
that we won't break consistency with the other `type_is` functions.
Implement `has_dtor` method in TypeContents

The patch also adds a `type_has_dtor` function to keep consistency with
the other functions present in this module.
Don't allow static items with `Drop`

Partially addresses #10577