[Enhancement]: Remove the CURRENT_TERM file when GC the entire table.

[thweetkomputer]

Current Behavior

To avoid reading while dropping a table across different nodes, a CURRENT_TERM is used. However, the CURRENT_TERM files cannot be deleted.

Proposed Improvement

After eloqstore support node group, use a lock for node group to control the creating and deleting of CURRENT_TERM.

[thweetkomputer]

CURRENT_TERM cannot prevent this scenario:

after a new eloqstore instance with higher term gc all data including manifest, the eloqstore with smaller term writes data. then new instance can read data written by the old one.