This PR ports a few changes from PBSS: - Fix the snapshot generator waiter in case the generation is not even initialized - Refactor db inspector for ancient store
* cmd, core, ethdb, node: create chain freezer in a sub folder * core/rawdb: remove unused code * core, ethdb, node: add AncientDatadir API back * cmd, core: extend freezer info dump for sub-ancient-store * core/rawdb: rework freezer inspector * core/rawdb: address comments from Peter * core/rawdb: fix build issue