Make infix modifier diagnostic message more informative (KT-12589)

(cherry picked from commit 2744309)

idea/testData/intentions/toInfixCall/multipleArguments.kt

@@ -1,5 +1,5 @@
 // IS_APPLICABLE: false
-// ERROR: 'infix' modifier is inapplicable on this function
+// ERROR: infix modifier is inapplicable on this function: must have a single value parameter
 interface Foo {
     infix fun foo(a: Int, b: Int)
 }

idea/testData/intentions/toInfixCall/namedArgument.kt

@@ -1,5 +1,5 @@
 // IS_APPLICABLE: false
-// ERROR: 'infix' modifier is inapplicable on this function
+// ERROR: infix modifier is inapplicable on this function: must have a single value parameter
 fun foo(x: Foo) {
     x.<caret>foo(bar = x)
 }

idea/testData/intentions/toInfixCall/noExplicitReceiver.kt

@@ -1,4 +1,4 @@
 // IS_APPLICABLE: false
-// ERROR: 'infix' modifier is inapplicable on this function
+// ERROR: infix modifier is inapplicable on this function: must be a member of an extension function
 infix fun id(s: String) = s
 val x = <caret>id("0").get(0)

idea/testData/intentions/toInfixCall/packageFunctionCall.kt

@@ -1,5 +1,5 @@
 // IS_APPLICABLE: false
-// ERROR: 'infix' modifier is inapplicable on this function
+// ERROR: infix modifier is inapplicable on this function: must be a member of an extension function
 package ppp
 
 infix fun foo(p: String){}

idea/testData/intentions/toInfixCall/secondParameterLabeled.kt

@@ -1,5 +1,5 @@
 // IS_APPLICABLE: false
-// ERROR: 'infix' modifier is inapplicable on this function
+// ERROR: infix modifier is inapplicable on this function: must have a single value parameter
 
 class Foo {
     infix fun foo(x: Int = 0, y: Int = 0) {

idea/testData/intentions/toInfixCall/simpleArgumentAndFunctionLiteralArgument.kt

@@ -1,5 +1,5 @@
 // IS_APPLICABLE: false
-// ERROR: 'infix' modifier is inapplicable on this function
+// ERROR: infix modifier is inapplicable on this function: must have a single value parameter
 
 fun foo(x: Foo) {
     x.<caret>foo(1) { it * 2 }

idea/testData/intentions/toInfixCall/singlePackageFunctionCall.kt

@@ -1,6 +1,6 @@
 // WITH_RUNTIME
 // IS_APPLICABLE: false
-// ERROR: 'infix' modifier is inapplicable on this function
+// ERROR: infix modifier is inapplicable on this function: must be a member of an extension function
 
 package demo