fix(config): fix memory safety, memory leaks, and add unit test coverage

• Fix an out-of-bounds/segmentation fault in config_getlist when parsing command-line options that do not specify bracket offsets (e.g. --rfsimulator.serveraddr). Added index bracket verification and guarded memcpy against NULL pointers on list reallocation.
• Initialize valid_idx to ParamList->numelt in config_getlist to properly support overriding and appending elements when a configuration file has existing array items.
• Fix memory leaks in end_configmodule
• Add test cases in test_config_cmdline.cpp

Signed-off-by: Bartosz Podrygajlo bartosz.podrygajlo@openairinterface.org and assisted-by Gemini