The seq_arr_erase_it function was modifying start_it during the free_func loop,
which led to incorrectly apply the free_func on the whole array.
This commit makes sure the elements "freed" are only those in the range and not the whole seq_arr.
* Fixes the logic by introducing a temporary iterator for the free loop,
preserving start_it and end_it for correct offset calculations.
* Adds a regression test in test_seq_arr to verify that only the selected
subrange is erased and that free_func is called exactly on that range.
In a later commit, we will use find_if in L2. In the case of building
with E2 agent, we link e2_agent which comes with its own implementation
of find_if_arr(), which results in a name clash. Rename the OAI
implementation, as nothing uses this, anyway.
Guido Casati