Provide std::vector interfaces for our user data functions

[holke]

Many of our users have their data in std::vector. To easen usage of t8code's user data handling functions, we should provide versions of them that accept std::vector instead of sc_array. In particular

t8_forest_iterate_replace
t8_forest_partition_data
t8_forest_ghost_exchange_data
t8_forest_search

The implementation is quick: Create an sc_array view of the vector and call the sc_array variant of the function.