Consider removing Create store from the flow, once Server admin has ability to set default store rate and currency

[pavlenex]

Once BTCPay Server itself, allows server admins to set default currency and rate source we should consider removing the create a store screen. We would be left with store name, and that one can just generically always be Store, since what actually matters is StoreID.

Removing this, wouldn't mean users can't configure them, since in settings we should allow them to change rate, store name and rate source.

Relevant issues:

btcpayserver/btcpayserver#5653

[dstrukt]

More than happy to remove any additional config from the initial setup, esp. on the App side of things.