FIR: add UnsafeCall resolution diagnostics

Previously unsafe call is reported as part of InapplicableWrongReceiver.
This makes it difficult for the downstream checkers to report different
diagnostics.

compiler/testData/diagnostics/tests/generics/nullability/expressionsBoundsViolation.fir.kt

@@ -13,7 +13,7 @@ fun <F : String?> bar(x: F) {
     foo1(<!ARGUMENT_TYPE_MISMATCH!>x<!>)
     foo1<F>(<!ARGUMENT_TYPE_MISMATCH!>x<!>)
 
-    x.<!INAPPLICABLE_CANDIDATE!>foo2<!>()
+    x<!UNSAFE_CALL!>.<!>foo2()
     x.<!INAPPLICABLE_CANDIDATE!>foo2<!><F>()
 }
 

compiler/testData/diagnostics/tests/generics/nullability/functionalBound.fir.kt

@@ -1,6 +1,6 @@
 fun <E : String?, T : ((CharSequence) -> Unit)?> foo(x: E, y: T) {
     if (x != null) {
-        <!INAPPLICABLE_CANDIDATE!>y<!>(x)
+        <!UNSAFE_IMPLICIT_INVOKE_CALL!>y<!>(x)
     }
 
     if (y != null) {

compiler/testData/diagnostics/tests/generics/nullability/smartCastRefinedClass.fir.kt

@@ -1,6 +1,6 @@
 fun <T : Any?> foo(x: T) {
     if (x is String?) {
-        x.<!INAPPLICABLE_CANDIDATE!>length<!>
+        x<!UNSAFE_CALL!>.<!>length
 
         if (x != null) {
             x.length

compiler/testData/diagnostics/tests/generics/nullability/smartCasts.fir.kt

@@ -24,7 +24,7 @@ fun <T : CharSequence?> foo(x: T) {
         x<!UNNECESSARY_SAFE_CALL!>?.<!>bar1()
     }
 
-    x.<!INAPPLICABLE_CANDIDATE!>length<!>
+    x<!UNSAFE_CALL!>.<!>length
 
     if (x is String) {
         x.length

compiler/testData/diagnostics/tests/generics/nullability/smartCastsOnThis.fir.kt

@@ -23,7 +23,7 @@ fun <T : String?> T.foo() {
         this<!UNNECESSARY_SAFE_CALL!>?.<!>bar1()
     }
 
-    <!INAPPLICABLE_CANDIDATE!>length<!>
+    <!UNSAFE_CALL!>length<!>
 
     if (this is String) {
         length

compiler/testData/diagnostics/tests/generics/nullability/tpInBounds.fir.kt

@@ -8,7 +8,7 @@ class A<T : CharSequence?, E1 : T, E2: T?> {
         x.bar()
 
         if (1 == 1) {
-            y.<!INAPPLICABLE_CANDIDATE!>bar<!>()
+            y<!UNSAFE_CALL!>.<!>bar()
         }
 
         x?.bar()

compiler/testData/diagnostics/tests/generics/nullability/useAsReceiver.fir.kt

@@ -7,7 +7,7 @@ fun CharSequence?.bar2() {}
 fun <T : CharSequence> T.bar3() {}
 
 fun <T : String?> foo(x: T) {
-    x.<!INAPPLICABLE_CANDIDATE!>length<!>
+    x<!UNSAFE_CALL!>.<!>length
     x?.length
 
     if (1 == 1) {
@@ -21,7 +21,7 @@ fun <T : String?> foo(x: T) {
     x?.bar1()
     x?.bar2()
 
-    x.<!INAPPLICABLE_CANDIDATE!>bar3<!>()
+    x<!UNSAFE_CALL!>.<!>bar3()
 
     x?.let { it.length }
 }