Add function registry for LPAD string function

Author: jpedroantunes

cpp/src/gandiva/function_registry_string.cc

@@ -134,6 +134,9 @@ std::vector<NativeFunction> GetStringFunctionRegistry() {
                      utf8(), kResultNullIfNull, "substr_utf8_int64",
                      NativeFunction::kNeedsContext),
 
+      NativeFunction("lpad", {}, DataTypeVector{utf8(), int32(), utf8()}, utf8(),
+                     kResultNullIfNull, "lpad", NativeFunction::kNeedsContext),
+
       NativeFunction("concatOperator", {}, DataTypeVector{utf8(), utf8()}, utf8(),
                      kResultNullIfNull, "concatOperator_utf8_utf8",
                      NativeFunction::kNeedsContext),