SCORU/Node: store and context versioning information

Context

This MR adds versioning information to the store and context of the rollup node. This allows to not run a rollup node on a store that has an incompatible format and to perform store migrations more easily.

Fixes #5554 (closed).

The store has a file in <data_dir>/storage/version which contains something like:

{ "store_version" : 1 }

and the context has an entry under the key /context_version which contains the context version (for now 0 as there has not been any non backward compatible changes in the context).

Depends in !8676 (merged) (store migrations).

Manually testing the MR

Run

dune exec tezt/tests/main.exe -- -f sc_rollup.ml store migration --keep-temp

and check that the files in <temp_dir>/1/sc-rollup-node1/storage/version contain

{ "store_version": 1 }