module api func: open container files

some updates lately have brought in functionality where module artifacts are directly opening tar files. we need to build a protected function the for API for modules to use when they need tar file contents. similar to `get_text_file_content` or `get_plist_content` funcs.

1. are there other compression types that a module might want to access?
2. do we make it a generic `get_compressed_file_contents` or similar?
3. anything else to consider?

see PR https://github.com/abrignoni/iLEAPP/pull/1187 for examples of accessing tar files