[FIR] Implement warnings for java nullability type mismatch on override

#KT-56989

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/jspecifyOld/warnMode/OverrideOfAnnotated.fir.kt

@@ -1,79 +0,0 @@
-// JSPECIFY_STATE: warn
-
-// FILE: Foo.java
-public interface Foo {}
-// FILE: BaseClass.java
-
-import org.jspecify.nullness.*;
-
-@NullMarked
-public class BaseClass {
-    public Foo everythingNotNullable(Foo x) { return null; }
-
-    public @Nullable Foo everythingNullable(@Nullable Foo x) { return null; }
-
-    public @NullnessUnspecified Foo everythingUnknown(@NullnessUnspecified Foo x) { return null; }
-
-    public @Nullable Foo mixed(Foo x) { return null; }
-
-    public Foo explicitlyNullnessUnspecified(@NullnessUnspecified Foo x) { return null; }
-}
-
-
-// FILE: main.kt
-
-private val FOO = object : Foo {}
-
-class Correct : BaseClass() {
-    override fun everythingNotNullable(x: Foo): Foo {
-        return FOO
-    }
-
-    override fun everythingNullable(x: Foo?): Foo? {
-        return null
-    }
-
-    override fun everythingUnknown(x: Foo?): Foo? {
-        return null
-    }
-
-    override fun mixed(x: Foo): Foo? {
-        return null
-    }
-
-    override fun explicitlyNullnessUnspecified(x: Foo): Foo {
-        return FOO
-    }
-}
-
-class WrongReturnTypes : BaseClass() {
-    override fun everythingNotNullable(x: Foo): Foo? {
-        return null
-    }
-
-    override fun explicitlyNullnessUnspecified(x: Foo): Foo? {
-        return null
-    }
-}
-
-class WrongParameter : BaseClass() {
-    override fun everythingNotNullable(x: Foo?): Foo {
-        return FOO
-    }
-
-    override fun everythingNullable(x: Foo): Foo? {
-        return null
-    }
-
-    override fun everythingUnknown(x: Foo): Foo? {
-        return null
-    }
-
-    override fun mixed(x: Foo?): Foo? {
-        return null
-    }
-
-    override fun explicitlyNullnessUnspecified(x: Foo?): Foo {
-        return FOO
-    }
-}

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/jspecifyOld/warnMode/OverrideOfAnnotated.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // JSPECIFY_STATE: warn
 
 // FILE: Foo.java