Update the balance provider for multiple APIs

[aaroncox]

• The balance provider concept needs to be abstracted out to accept different APIs
• The bloks.io API components need to be made into an individual provider.
• A balance provider for the light API needs to be created
• The configuration of a chain should allow us to specify which balance provider is used

The balance provider now:

https://github.com/greymass/unicove/blob/dev/src/stores/balances-provider.ts

The balance provider already starts abstracting it a bit here:

https://github.com/greymass/unicove/blob/dev/src/stores/balances-provider.ts#L61-L69

The bloks.io API code is just generic and placed in the same file. It should named better and potentially in its own file as a standardized interface. The light api code should then be created in a similar way with the same interface.