feat: revert changes to AccountProvider and add Bip44AccountProvider type alias (#361)

What is the current state of things and why does it need to change? 
1. It was determined that `AccountProviderType` doesn't work well with
the concept of a custom provider. We wanted to let the
`MultichainAccountWallet` orchestrate the discovery so it was determined
it would be better to keep the function signature as is for
`discoverAndCreateAccounts`.
2. Writing `AccountProvider<Bip44Account<KeyringAccount>>` is a
mouthful.
 
What is the solution your changes offer and how does it work? 
1. Remove the `AccountProviderType` enum, revert the changes made to
`AccountProvider`.
2. Write a type alias: `Bip44AccountProvider`.

Author: hmalik88

packages/account-api/src/api/provider.test.ts

@@ -1,19 +1,11 @@
 import type { EntropySourceId, KeyringAccount } from '@metamask/keyring-api';
 
-export enum AccountProviderType {
-  Evm = 'Evm',
-  Solana = 'Solana',
-  Btc = 'Btc',
-}
+import type { Bip44Account } from './bip44';
 
 /**
  * An account provider is reponsible of providing accounts to an account group.
  */
 export type AccountProvider<Account extends KeyringAccount> = {
-  /**
-   * The type of the provider.
-   */
-  providerType: AccountProviderType;
   /**
    * Gets an account for a given ID.
    *
@@ -43,15 +35,28 @@ export type AccountProvider<Account extends KeyringAccount> = {
   }) => Promise<Account[]>;
 
   /**
-   * Discover accounts for a given entropy source.
+   * Discover accounts for a given entropy source and a given group
+   * index.
    *
    * NOTE: This method needs to also create the discovered accounts.
    *
    * @param options - Options.
    * @param options.entropySource - Entropy source to use.
+   * @param options.groupIndex - Group index to use.
    * @returns The list of discovered and created accounts.
    */
   discoverAndCreateAccounts: (options: {
     entropySource: EntropySourceId;
+    groupIndex: number;
   }) => Promise<Account[]>;
 };
+
+/**
+ * A BIP-44 provider is a provider that can provide BIP-44 compatible accounts.
+ *
+ * Note: This is an alias for the `AccountProvider` type, but with a more specific
+ * type for the account.
+ */
+export type Bip44AccountProvider = AccountProvider<
+  Bip44Account<KeyringAccount>
+>;