[FEATURE]: Allow partial migrations

### Feature hasn't been suggested before.

- [x] I have verified this feature I'm about to request hasn't been suggested before.

### Describe the enhancement you want to request

Using the `migrate()` function, like you would with Cloudflare Durable Objects, you either apply all migrations, or none—there's no middle ground.

In that environment there's cases where you'd want to apply some migrations, run some logic, and only then resume with the rest of the migrations. Currently I call `migrate` as such:

```ts
await migrate(this.db, migrations);
```

but I would like to specify what is the last migration to apply, before resuming.