[data][experiment] Recods implementation via opaque types

[road21]

This is an idea how to implement records via opaque types (syntax works with help of structural typing and conversion).

Currently there are two blockers to make it work:

• too slow compilation for fat records (compiler bug very slow compilation of extension methods for opaque types scala/scala3#25352)
• no way to override equals / hashCode methods (need separate method like is for Dict)

[fwbrasil]

Nice! It'd be great to avoid the wrapper allocation. We already have a few APIs that are opaque types and don't provide hashCode and equals like Span. We recommend enabling strict equality due to that.

[road21]

It'd be great to avoid the wrapper allocation

fixed this