Do not disable 'redundant visibility modifier' inspection completely in Explicit API mode.

Instead, disable it only for effectively public declarations.

Add tests for this IDE inspection.

compiler/testData/diagnostics/testsWithExplicitApi/mustBeEffectivelyPublic.kt

@@ -1,3 +1,20 @@
 private class Foo {
     fun method() {}
+}
+
+public interface I {
+    public fun bar()
+}
+
+public fun f() {
+    val i = object : I {
+        internal var foo = 0
+        override fun bar() {}
+    }
+    i.foo = 1
+
+    class LocalClass {
+        internal var foo = 0
+    }
+    LocalClass().foo = 1
 }

compiler/testData/diagnostics/testsWithExplicitApi/mustBeEffectivelyPublic.txt

@@ -1,5 +1,7 @@
 package
 
+public fun f(): kotlin.Unit
+
 private final class Foo {
     public constructor Foo()
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
@@ -7,3 +9,10 @@ private final class Foo {
     public final fun method(): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
+
+public interface I {
+    public abstract fun bar(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}