This is a preparation for #8022, to make the PR both backwards and
foward compatible.
This commit adds `eviction_state` field to control file. Adds support
for reading it, but writes control file in old format where possible, to
keep the disk format forward compatible.
Note: in `patch_control_file`, new field gets serialized to json like
this:
- `"eviction_state": "Present"`
- `"eviction_state": {"Offloaded": "0/8F"}`
f45cf28247