FTS-1923: Turn configurable eviction flag into skip-eviction in order to not perform file release for Storage Element

This merge request changes the fts_url_copy process to add a new option called --skip-eviction which tells the fts_url_copy to not evict the source file after a transfer even if it has a bring-online token.

Since the previous behavior was to only evict the source file when the --evict flag was present, this merge request also removes the obsolete --evict flag.

The merge request also changes the mechanism through which the return status of the "evict" call is sent to monitoring messages (FTS-1800). Since the eviction call is now executed at the fts_url_copy level and not in the Gfal2 level, the status code of the eviction call no longer comes from the GFAL_EVICT_EVENT, but rather by the error status of the gfal2_release() function.

The database schema was also modified to allow storage elements (SE) to be configured with respect to their "skip eviction" status. A method to read this configuration from the DB and set it in the fts_url_copy process was also added