method_handles: Minor refactor of PerformArgumentConversions.

Separate out a method that can perform a single argument conversion.
Useful for Field setters and also for future use in transforming handles
where the input source will not be a stack frame.

Also remove unnecessary JValue* argument.

bug: 30550796
Test: make test-art-host
Change-Id: I75a63800839dbf1016a2c362169e138c83f34e4c
diff --git a/runtime/interpreter/interpreter_common.cc b/runtime/interpreter/interpreter_common.cc
index b71236b..72722dd 100644
--- a/runtime/interpreter/interpreter_common.cc
+++ b/runtime/interpreter/interpreter_common.cc
@@ -795,7 +795,7 @@
         self, new_shadow_frame, StackedShadowFrameType::kShadowFrameUnderConstruction);
     if (!PerformArgumentConversions<is_range>(self, callsite_type, target_type,
                                               shadow_frame, vregC, first_dest_reg,
-                                              arg, new_shadow_frame, result)) {
+                                              arg, new_shadow_frame)) {
       DCHECK(self->IsExceptionPending());
       result->SetL(0);
       return false;