Add ability to disable migrations for Session Storage Adapter for Redis

[robnielsen-il]

Currently, there is no way to disable migrations for Session Storage Adapter for Redis. In most cases this is unnecessary and also doesn't work with AWS Redis since it doesn't support the Redis function keys(). The function keys() is used by the function migrateAddShopKeyToTrackSessionsByShop in shopify-app-session-storage-redis/src/migrations.ts

This request is to add an optional parameter to RedisSessionStorage() to disable calling this.migrator.applyMigrations(this.internalInit).