Standardize context receiver parameter names

Previously, FIR used `_context_receiver_n` while FE10 used `<this>` for
all context receiver parameters. This commit changes the code in FE10
to follow the convention from FIR.

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt

@@ -1157,7 +1157,7 @@ class Fir2IrDeclarationStorage(
         return contextReceiver.convertWithOffsets { startOffset, endOffset ->
             irFactory.createValueParameter(
                 startOffset, endOffset, IrDeclarationOrigin.DEFINED, IrValueParameterSymbolImpl(),
-                Name.identifier("_context_receiver_$index"), index, type,
+                NameUtils.contextReceiverName(index), index, type,
                 null,
                 isCrossinline = false, isNoinline = false,
                 isHidden = false, isAssignable = false