Fix deepcopy for generics

[Jefftree]

We had a regression with the deepcopy gen not being able to handle generic fields.

type Foo struct {
   field set.Set[string]
}

This fixes the name to not be trimmed for generics in goNameToName and also fixes a bug with named interfaces capturing generics not capturing generics properly.

[thockin]

verified against k/k - this function seems like a great target for a unit test

[Jefftree]

/assign @thockin
/cc @TheSpiritXIII

Updated with fixes.

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In response to this:

/assign @thockin
/cc @TheSpiritXIII

Updated with fixes.

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[Jefftree]

This change is optional but I figured it'd be more useful to use cmp.Diff instead of a two complex structs that are quite hard to read in the tests. k/k already has this dependency https://github.com/kubernetes/kubernetes/blob/master/go.mod#L38 so we are not adding anything new for them.

[thockin]

Thanks!

/lgtm
/approve

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This pull-request has been approved by: Jefftree, thockin

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