Identify workaround for dropped specialisation

[bishabosha]

Dotty removes support for the @specialized annotation, but introduces specialising inline methods. This brings up some issues:

• can we make specialised code generic, with support for specialised typeclasses
• can we minimise any new boilerplate
• can strong type inference be preserved

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With Dotty comes prior mentioned inline methods, along with improved GADT reasoning which can be used to select a specialised method.

[bishabosha]

I'll publish soon some experimentation I've been working on.