FIR: Rework receivers processing in resolution

- Put extensionReceiver to candidate even if it's explicit (for sake of clarity)
- Split CheckReceiver (dispatch part should only check nullability)

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) {
-        y(x)
+        <!INAPPLICABLE_CANDIDATE!>y<!>(x)
     }
 
     if (y != null) {
@@ -10,4 +10,4 @@ fun <E : String?, T : ((CharSequence) -> Unit)?> foo(x: E, y: T) {
     if (x != null && y != null) {
         y(x)
     }
-}
+}

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

@@ -1,6 +1,6 @@
 fun <T : Any?> foo(x: T) {
     if (x is String?) {
-        x.length
+        x.<!INAPPLICABLE_CANDIDATE!>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?.bar1()
     }
 
-    x.length
+    x.<!INAPPLICABLE_CANDIDATE!>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?.bar1()
     }
 
-    length
+    <!INAPPLICABLE_CANDIDATE!>length<!>
 
     if (this is String) {
         length
@@ -33,4 +33,4 @@ fun <T : String?> T.foo() {
         bar2()
         bar3()
     }
-}
+}

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.length
+    x.<!INAPPLICABLE_CANDIDATE!>length<!>
     x?.length
 
     if (1 == 1) {