Fix #10098: Handle inheritance for implicitNotFound annotation

[prolativ]

No description provided.

[dottybot]

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[prolativ]

This PR fixes the issue by making the behaviour like in scala 2.13. However there are some corner cases handled in neither version e.g.

trait Foo
trait Bar extends (Foo @annotation.implicitNotFound("Custom message"))
object Test {
  implicitly[Bar]
}

Should the custom message be displayed here?

[smarter]

No, that's fine, the documentation of https://www.scala-lang.org/api/2.13.3/scala/annotation/implicitNotFound.html states where the annotation has an effect and that doesn't include parent clauses.

[prolativ]

PR ready for merge then