Box bounded arguments of HKT result types in Java generic signatures

[SolalPirelli]

Fixes #26786

Have you relied on LLM-based tools in this contribution?

No

How was the solution tested?

New automated tests (including the issue's reproducer, if applicable)

[WojciechMazur]

Found 1 more failure, this this in reactivecore/usql, it's tiny, but results in similar failure, can you check it out as well / include in tests?

@throws[IllegalArgumentException]("x")
class A

scala-cli compile repro/reactivecore/usql/test.scala -S 3.nightly --server=false
Error while emitting A
^ (of class java.lang.Character)
1 error found
Compilation failed

I think it also fails withou ("x")