IC mangling: Change mangling rules

1. Use 'x' for each parameter, which is not an inline class, every
possible clash is handled by signature rather than name. This change
makes more API changes binary-compatible. So, the changes are in line
with the vision of inline classes are value classes, like primitives.

2. Take return type into account when mangling a function if the return
type is inline class. Otherwise, boxing bridge will not be generated,
which leads to CCE at runtime.

compiler/testData/codegen/bytecodeListing/kt42879.txt

@@ -19,7 +19,7 @@ public final class A {
 @kotlin.Metadata
 public interface I {
     // source: 'kt42879.kt'
-    public abstract method compute-GKOAj6k(p0: int): int
+    public abstract method compute-WzO2ekY(p0: int): int
 }
 
 @kotlin.Metadata
@@ -30,7 +30,7 @@ final class Kt42879Kt$g$1 {
     inner (anonymous) class Kt42879Kt$g$1
     static method <clinit>(): void
     method <init>(): void
-    public final method compute-GKOAj6k(p0: int): int
+    public final method compute-WzO2ekY(p0: int): int
 }
 
 @kotlin.Metadata