api: internal: Use RAV1E_DATA_PATH for storing the importance
api: internal: Use RAV1E_DATA_PATH for storing the importance

Right now the dump is being stored in the dir when the command is
running, which is not the right way to store things, with this
commit, at RAV1E_DATA_PATH location, dumped items will be
stored, if it is not provided, it will be stored at
$PWD/.lookahead_data/ location.

xiph/rav1e,xiph/rav1e