FIR checker: differentiate UNSAFE_CALL from INAPPLICABLE_CANDIDATE

To do so, inside the root cause of inapplicable candidate errors,
we will record expected/actual type of receiver, if any.
That will help identifying inapplicable calls on nullable receiver.

compiler/testData/diagnostics/tests/resolve/invoke/errors/unsafeCallWithInvoke.fir.kt

@@ -4,7 +4,7 @@
 operator fun String.invoke(i: Int) {}
 
 fun foo(s: String?) {
-    <!INAPPLICABLE_CANDIDATE!>s<!>(1)
+    <!UNSAFE_CALL!>s<!>(1)
 
-    <!INAPPLICABLE_CANDIDATE!>(s ?: null)(1)<!>
+    <!UNSAFE_CALL!>(s ?: null)(1)<!>
 }

compiler/testData/diagnostics/tests/resolve/invoke/implicitInvokeAfterSafeCall.fir.kt

@@ -12,7 +12,7 @@ class Another1 {
 
 fun Another1.main(x: Bar1<String>?) {
     x?.value {}
-    x?.value.<!INAPPLICABLE_CANDIDATE!>invoke<!>({})
+    x?.value.<!UNSAFE_CALL!>invoke<!>({})
 }
 
 // Test case 2: additional receiver, non-generic invoke
@@ -26,7 +26,7 @@ class Another2 {
 
 fun Another2.main(x: Bar2<String>?) {
     x?.value(1)
-    x?.value.<!INAPPLICABLE_CANDIDATE!>invoke<!>(1)
+    x?.value.<!UNSAFE_CALL!>invoke<!>(1)
 }
 
 // Test case 3: additional generic receiver, generic invoke
@@ -40,7 +40,7 @@ class Another3<T> {
 
 fun <K> Another3<K>.main(x: Bar3<K>?) {
     x?.value(1)
-    x?.value.<!INAPPLICABLE_CANDIDATE!>invoke<!>(1)
+    x?.value.<!UNSAFE_CALL!>invoke<!>(1)
 }
 
 // Test case 4: additional receiver, generic invoke with nullable receiver
@@ -68,7 +68,7 @@ class Another5 {
 
 fun Another5.main(x: Bar5?) {
     x?.value {}
-    x?.value.<!INAPPLICABLE_CANDIDATE!>invoke<!>({})
+    x?.value.<!UNSAFE_CALL!>invoke<!>({})
 }
 
 // Test case 6: top-level generic invoke
@@ -96,7 +96,7 @@ operator fun <T> Foo7<T>.invoke(x: Int) {}
 
 fun Another7.main(x: Bar7<String>?) {
     x?.value(1)
-    x?.value.<!INAPPLICABLE_CANDIDATE!>invoke<!>(1)
+    x?.value.<!UNSAFE_CALL!>invoke<!>(1)
 }
 
 // Test case 8: top-level non-generic invoke
@@ -136,5 +136,5 @@ class Another10 {
 
 fun Another10.main(x: Bar10<String>?) {
     x?.value {}
-    x?.value.<!INAPPLICABLE_CANDIDATE!>invoke<!>({})
+    x?.value.<!UNSAFE_CALL!>invoke<!>({})
 }

compiler/testData/diagnostics/tests/resolve/invoke/invokeAndSmartCast.fir.kt

@@ -7,8 +7,8 @@ fun test(a: A) {
         (a.x)("")
     }
     "".<!UNRESOLVED_REFERENCE!>(a.x)()<!>
-    a.<!INAPPLICABLE_CANDIDATE!>x<!>("")
-    <!INAPPLICABLE_CANDIDATE!>(a.x)("")<!>
+    a.<!UNSAFE_CALL!>x<!>("")
+    <!UNSAFE_CALL!>(a.x)("")<!>
 
     with("") {
         a.<!INAPPLICABLE_CANDIDATE!>x<!>()

compiler/testData/diagnostics/tests/resolve/invoke/kt30695_2.fir.kt

@@ -14,7 +14,7 @@ class MemberInvokeOwner {
 
 class Cls {
     fun testImplicitReceiver() {
-        <!INAPPLICABLE_CANDIDATE!>nullableExtensionProperty<!>()
+        <!UNSAFE_CALL!>nullableExtensionProperty<!>()
     }
 }
 
@@ -30,7 +30,7 @@ fun testNullableReceiver(nullable: Cls?) {
 }
 
 fun testNotNullableReceiver(notNullable: Cls) {
-    notNullable.<!INAPPLICABLE_CANDIDATE!>nullableExtensionProperty<!>()
+    notNullable.<!UNSAFE_CALL!>nullableExtensionProperty<!>()
     notNullable?.extensionProperty()
 }
 
@@ -38,6 +38,6 @@ fun testFlexibleReceiver() {
     val flexible = JavaClass.createFlexible()
     flexible.extensionProperty()
     flexible?.extensionProperty()
-    flexible.<!INAPPLICABLE_CANDIDATE!>nullableExtensionProperty<!>()
-    flexible?.<!INAPPLICABLE_CANDIDATE!>nullableExtensionProperty<!>()
+    flexible.<!UNSAFE_CALL!>nullableExtensionProperty<!>()
+    flexible?.<!UNSAFE_CALL!>nullableExtensionProperty<!>()
 }