* Rename `provider` to `providerConfig`
The network controller `provider` state has been renamed to
`providerConfig`. This better reflects what this state is, and makes
this controller more closely aligned with the core network controller.
All references to the provider configuration have been updated to
prefer `providerConfig` over `provider`, to make the distinction clear
between a provider and provider config.
Closes#18902
* Add migration
The provider configuration selector has been renamed from `getProvider`
to `getProviderConfig`, and it has been moved from the selectors module
into the MetaMask slice. A JSDoc description has been added as well.
This refactor was done to make a future PR simpler, and to make this
selector better aligned with best practices.
This relates to #18902
