* Properly resize arrays when adding
The current logic attempts to update the array but, because
append may need to allocate a new array with adequate space,
the code can currently leave dest referring to the old,
under-sized array. The solution is to use the set(dest)
logic that already exists and is used for the IsNull case.
Added a test case that would fail before this fix and now passes.
This fixespulumi/pulumi#5871.
* Add CHANGELOG entry
This function adds a property value to another property at a given path,
creating containing properties as required. If the property cannot be
added because of a mismatch between the value types required by the path
and the values present in the destination, the add will fail. If a value
already exists at the given path, the add will succeed.
Related to #1635.
