Currently, since the data_value(bool) ctor
is implicit, pointers of any kind are implicitly
convertible to data_value via intermediate conversion
to `bool`.
This is error prone, since it allows unsafe comparison
between e.g. an `sstring` with `some*` by implicit
conversion of both sides to `data_value`.
For example:
```
sstring name = "dc1";
struct X {
sstring s;
};
X x(name);
auto p = &x;
if (name == p) {}
```
Refs #17261
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Closesscylladb/scylladb#17262