[DB migrations] Consider inserting data after DB migrations not during DB migration

[jonastheis]

The SeaORM migrations and specifically the MigratorTrait are statically typed. By default, the framework doesn't allow for passing dynamic data to the individual migrations.

Currently, this is solved via static types returning constant data via the MigrationInfo trait. However, this is very limiting as all data needs to be known at compile time.

In the context of implementing #250 this became a problem: the genesis hash is not constant but it is dynamic depending on the ChainSpec which is read at runtime during node startup.

For now this is solved by overriding the genesis hash after the migrations ran. But overall we should reconsider how we populate data into the DB as the current mechanism is already reaching its limits.

[Thegaram]

I agree. During node startup, we should first run the migrations (chain-agnostic), then insert any data, just like we do it here.

rollup-node/crates/node/src/args.rs

Lines 209 to 213 in e2f7f95

	// insert the custom chain genesis hash into the database
	let genesis_hash = chain_spec.genesis_hash();
	db.insert_genesis_block(genesis_hash)
	.await
	.expect("failed to insert genesis block (custom chain)");