fix: Merge custom context in correct order

When adding a variable to a custom context then the variable is wrapped in a static context and both contexts are combined.

The combined context contains all variables in the order: custom context and then static context with new variable. On accessing a variable from the combined context, it looks for the variable in the custom context first. As a result, the new variable can't be accessed if a variable with the same name exists in the custom context.

The behavior is different for a static context. The new variable is added to the static context and overrides a previous variable with the same name.

Align the behavior for a custom context with the behavior of a static context. A new variable should override/shadow an existing variable.

(cherry picked from commit 626aa4d)

src/main/scala/org/camunda/feel/impl/interpreter/EvalContext.scala

@@ -175,7 +175,7 @@ object EvalContext {
       case (StaticVariableProvider(thisVariables), StaticVariableProvider(otherVariables)) =>
         StaticVariableProvider(thisVariables ++ otherVariables)
       case (thisProvider, otherProvider)                                                   =>
-        CompositeVariableProvider(List(thisProvider, otherProvider))
+        CompositeVariableProvider(List(otherProvider, thisProvider))
     }
   }
 
@@ -195,7 +195,7 @@ object EvalContext {
         StaticFunctionProvider(allFunctions)
       }
       case (thisProvider, otherProvider)                                                   =>
-        CompositeFunctionProvider(List(thisProvider, otherProvider))
+        CompositeFunctionProvider(List(otherProvider, thisProvider))
     }
   }