feat: add driver option to get around issues with useFactory and inject

[B4nan]

When you try to inject the EntityManager or MikroORM symbols exported from the driver package, Nest.js needs to be aware of those typed. In other words, those driver specific exports need to be specifically registered in the DI container. This module uses automated discovery of the driver type in order to do that, but it fails to work when you use useFactory which requires some dependencies.

Instead of relying on this discovery, you can provide the driver type explicitly:

@Module({
  imports: [
    MikroOrmModule.forRootAsync({
      useFactory: (configService: ConfigService) => configService.getOrThrow(ConfigKey.ORM),
      inject: [ConfigService],
      driver: PostgreSqlDriver,
    }),
  ],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

Closes #184
Closes #195