Change NO_EXPLICIT_VISIBILITY_IN_API_MODE diagnostic range to 'declaration modifiers + name'.

Motivation: missing visibility modifier is an error in visibility modifiers list, so we should highlight this list.
Including a name in the range is convenient for using alt+enter (you don't have to move cursor from name to fun/class/val keyword)

 Also change NO_EXPLICIT_RETURN_TYPE_IN_API_MODE diagnostic range to 'declaration name' to match corresponding IDE inspection.

Fix stylistic problems and typos after review

compiler/testData/diagnostics/testsWithExplicitApi/constructors.kt

@@ -1,10 +1,12 @@
+// SKIP_TXT
+
 public class Foo1 () {}
 public class Foo2 constructor() {}
 public class Foo3 public constructor() {}
 public class Foo4 private constructor() {}
 
 public class Foo5 {
-    <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>constructor()<!> {}
+    <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>constructor<!>() {}
 }
 
 public class Foo6 {