[lua] Fix redundant _hx_funcToField for non-function fields

[jdonaldson]

Summary

Fixes #11842. Non-function fields were being unnecessarily wrapped with _hx_funcToField during assignment.

Problem

When assigning fields between anonymous types (typedefs), the Lua generator wrapped all assignments with _hx_funcToField, even for non-function types like Int:

typedef Slot = { var data: Int; }

// This generated: a.data = _hx_funcToField(b.data)
a.data = b.data;

Fix

Added is_function_type e2.etype guards to three patterns in genlua.ml that were missing them. The fourth pattern (for TLocal assignments) already had this check.

Test plan

• Added unit test testNoFuncToFieldForNonFunctions in TestLua.hx
• All 11520 Lua unit tests pass