[FIR] Improve diagnostic reporting & don't use error symbol for candidate if possible

Also introduce few new diagnostics:
- NONE_APPLICABLE more many inapplicable candidates
- HIDDEN for visible candidates

compiler/testData/diagnostics/tests/smartCasts/intersectionScope/unstableSmartCast.fir.kt

@@ -33,6 +33,6 @@ fun test() {
         x.baz(1).checkType { _<Unit>() }
         x.<!INAPPLICABLE_CANDIDATE!>baz<!>(1, 2)
 
-        x.<!UNRESOLVED_REFERENCE!>foobar<!>().<!INAPPLICABLE_CANDIDATE!>checkType<!> { <!UNRESOLVED_REFERENCE!>_<!><String>() }
+        x.<!UNRESOLVED_REFERENCE!>foobar<!>().<!INAPPLICABLE_CANDIDATE!>checkType<!> { <!INAPPLICABLE_CANDIDATE!>_<!><String>() }
     }
 }

compiler/testData/diagnostics/tests/smartCasts/objectLiterals/exclexcl.fir.kt

@@ -16,7 +16,7 @@ fun foo(): Int {
         k.run()
         val d: Int = c
         // a is not null because of k constructor, but we do not know it
-        return a <!INAPPLICABLE_CANDIDATE!>+<!> d
+        return a <!NONE_APPLICABLE!>+<!> d
     }
     else return -1
 }

compiler/testData/diagnostics/tests/smartCasts/objectLiterals/exclexclArgument.fir.kt

@@ -11,7 +11,7 @@ fun foo(): Int {
         }
         k.run()
         val d: Int = c
-        return a <!INAPPLICABLE_CANDIDATE!>+<!> d
+        return a <!NONE_APPLICABLE!>+<!> d
     }
     else return -1
 }

compiler/testData/diagnostics/tests/smartCasts/objectLiterals/exclexclTwoArgument.fir.kt

@@ -15,7 +15,7 @@ fun foo(): Int {
         }
         k.run()
         val d: Int = c
-        return a <!INAPPLICABLE_CANDIDATE!>+<!> d
+        return a <!NONE_APPLICABLE!>+<!> d
     }
     else return -1
 }

compiler/testData/diagnostics/tests/smartCasts/safecalls/nullableReceiver.fir.kt

@@ -6,8 +6,8 @@ fun test(foo: Foo?) {
         // Error, foo?.bar is nullable
         it.<!INAPPLICABLE_CANDIDATE!>length<!>
         // Error, foo is nullable
-        foo.<!INAPPLICABLE_CANDIDATE!>bar<!>.<!UNRESOLVED_REFERENCE!>length<!>
+        foo.<!INAPPLICABLE_CANDIDATE!>bar<!>.length
         // Correct
         foo?.bar?.length
     }
-}
+}

compiler/testData/diagnostics/tests/smartCasts/safecalls/nullableReceiverInLongChain.fir.kt

@@ -13,13 +13,13 @@ fun test(foo: Foo?) {
         // Error, foo?.bar?.gav is nullable
         it.<!INAPPLICABLE_CANDIDATE!>length<!>
         // Error, foo is nullable
-        foo.<!INAPPLICABLE_CANDIDATE!>bar<!>.<!UNRESOLVED_REFERENCE!>gav<!>.<!UNRESOLVED_REFERENCE!>length<!>
+        foo.<!INAPPLICABLE_CANDIDATE!>bar<!>.gav.length
         // Correct
         foo?.bar?.gav?.length
     }
     foo?.bar?.gav.call { it }?.notNullLet {
         foo.<!INAPPLICABLE_CANDIDATE!>hashCode<!>()
-        foo.<!INAPPLICABLE_CANDIDATE!>bar<!>.<!UNRESOLVED_REFERENCE!>hashCode<!>()
+        foo.<!INAPPLICABLE_CANDIDATE!>bar<!>.hashCode()
     }
 }
 

compiler/testData/diagnostics/tests/smartCasts/smartcastOnSameFieldOfDifferentInstances.fir.kt

@@ -5,7 +5,7 @@ class A(val x: String?) {
     fun foo(other: A) {
         when {
             x == null && other.x == null -> "1"
-            x.<!INAPPLICABLE_CANDIDATE!>length<!> <!UNRESOLVED_REFERENCE!>><!> 0 -> "2"
+            x.<!INAPPLICABLE_CANDIDATE!>length<!> > 0 -> "2"
         }
     }
 }

compiler/testData/diagnostics/tests/smartCasts/varnotnull/plusplusMinusminus.fir.kt

@@ -12,10 +12,10 @@ operator fun Long?.inc() = this?.let { it + 1 }
 fun bar(arg: Long?): Long {
     var i = arg
     if (i++ == 5L) {
-        return i<!INAPPLICABLE_CANDIDATE!>--<!> <!INAPPLICABLE_CANDIDATE!>+<!> i
+        return i<!INAPPLICABLE_CANDIDATE!>--<!> + i
     }
     if (i++ == 7L) {
-        return i++ <!INAPPLICABLE_CANDIDATE!>+<!> i
+        return i++ <!NONE_APPLICABLE!>+<!> i
     }
     return 0L
-}
+}

compiler/testData/diagnostics/tests/smartCasts/varnotnull/unnecessaryWithMap.fir.kt

@@ -14,8 +14,8 @@ class MyClass {
         var res = 0
         m = create()
         // See KT-7428
-        <!INAPPLICABLE_CANDIDATE, UNRESOLVED_REFERENCE, UNRESOLVED_REFERENCE!>for ((k, v) in m)
-            <!UNRESOLVED_REFERENCE!>res += (k.<!UNRESOLVED_REFERENCE!>length<!> + v.<!UNRESOLVED_REFERENCE!>length<!>)<!><!>
+        <!INAPPLICABLE_CANDIDATE!>for ((k, v) in m)
+            res += (k.length + v.length)<!>
         return res
     }
-}
+}

compiler/testData/diagnostics/tests/smartCasts/varnotnull/varIntNull.fir.kt

@@ -2,5 +2,5 @@
 fun foo(): Int {
     var i: Int? = 42
     i = null
-    return i <!INAPPLICABLE_CANDIDATE!>+<!> 1
-}
+    return i <!NONE_APPLICABLE!>+<!> 1
+}