parachain db versioning (#2829)

* move parachains_db.rs to a module

* parachain versioning

* fixes

* more fixes

* Update node/service/src/parachains_db/upgrade.rs

* fix web-wasm check

* suggested style fixes

Co-authored-by: Bastian Köcher <[email protected]>

* Update node/service/src/parachains_db/upgrade.rs

* compilation fixes

Co-authored-by: Bastian Köcher <[email protected]>