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

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:

https://github.com/btcpayserver/btcpayserver/issues/5653

Start by reviewing the create store screen and the related BTCPay Server issue 5653, since this change depends on server-admin defaults for currency and rate source. The work is done when the flow no longer requires configuring those values, while settings still allow users to change the rate, store name, and rate source.

Written by the indexing model from the issue text.