Correctly handle limit on int4 and int8 types in PG

PG doesn't register it's types using the `int(4)` format that others do.
As such, if we alias `int8` to the other integer types, the range
information is lost. This is fixed by simply registering it separately.

The other option (which I specifically chose to avoid) is to pass the
information of the original type that was being aliased as an argument.
I'd rather avoid that, since an alias should truly be treated the same.
If we need different behavior for a different type, we should explicitly
register it with that, and not have a conditional based on aliasing.

Fixes #18144

[Sean Griffin & ysbaddaden]
Don't calculate all in-place changes to determine if attribute_changed?

Calling `changed_attributes` will ultimately check if every mutable
attribute has changed in place. Since this gets called whenever an
attribute is assigned, it's extremely slow. Instead, we can avoid this
calculation until we actually need it.

Fixes #18029