[FEATURE]: operator function for `is distinct from` (SQL:1999 standard T151)

### Describe what you want

This is useful for comparing two values where one of them may be null. The `=` operator used by `eq(` and the `not` operator from `not(` both return null when any input is null.

As a result, to compare a potentially null column to a value, you need to do, e.g. for checking non-equality:
```ts
or(isNull(myColumn), not(eq(myColumn, "myValue")))
```

It would be great to have a function to allow us to do e.g. `distinct(myColumn, "myValue")` which would generate `myColumn is distinct from 'myValue'`, therefore handling the null check and the equality check in a single condition.