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 <bkchr@users.noreply.github.com> * Update node/service/src/parachains_db/upgrade.rs * compilation fixes Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>