Add PRAGMA metadata_info that displays info about the storage of metadata, and correctly write free metadata blocks

[Mytherin]

This PR adds the PRAGMA metadata_info command that can be used to query information about the metadata manager:

D PRAGMA metadata_info;
┌──────────┬──────────────┬─────────────┬────────────────────────────────────────────┐
│ block_id │ total_blocks │ free_blocks │                 free_list                  │
│  int64   │    int64     │    int64    │                  int64[]                   │
├──────────┼──────────────┼─────────────┼────────────────────────────────────────────┤
│        0 │           64 │          61 │ [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14…  │
└──────────┴──────────────┴─────────────┴────────────────────────────────────────────┘

In addition, this PR fixes an issue found in #8943 where the free list of the metadata manager was not correctly serialized causing small leaking of storage space for every database restart.