Make test checking for conversion to param

[rylev]

@cherryleafroad @kennykerr perhaps I'm not understanding #1618, but I believe that the desired impl is already present and this PR adds a test that confirms that.

[MolotovCherry]

I'm using 0.34.0. Maybe it has changed since then? (I can share my actual code if needed)

Edit: I think I see what's going on. Your p is the trait ICustomPersistMemory. What I was doing, the equivalent in your example, was using struct Persist. Maybe I was doing it wrong

Edit 2:: I do indeed see the IntoParam on the trait itself as you've said

[rylev]

Yes, passing the implementation (in this case Persist) would be incorrect since it is a backing implementation and not itself an interface.

[kennykerr]

Ah yes, I forgot that was there already. Thanks for adding the test! 😜