[php-src] PR #25155: ext/dba: Fix request memory kept in persistent dba handles

Pull Request: https://github.com/php/php-src/pull/25155 Author: iliaal A dba_popen() handle outlives the request, but flatfile kept its last key buffer, inifile its current and last-fetched lines, and cdb_make its hash list in it as emalloc'd memory that the next request or the shutdown-time close then freed or read. flatfile now frees the key right away and uses its file position as the iteration marker; inifile and cdb_make allocate what they keep with the handle's persistence. cdb (read), lmdb, db1-db4, dbm, ndbm, gdbm, qdbm and tcadb keep only offsets, library cursors or malloc()ed buffers between calls.