feat: add getAccount action to AccountsController (#1892)

## Explanation

This PR adds getAccount action to the AccountsController.

## References

## Changelog

### `@metamask/package-a`

- **ADDED**: adds getAccount action to the AccountsController
## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [x] I've highlighted breaking changes using the "BREAKING" category
above as appropriate

packages/accounts-controller/src/AccountsController.test.ts

@@ -1841,6 +1841,7 @@ describe('AccountsController', () => {
       jest.spyOn(AccountsController.prototype, 'updateAccounts');
       jest.spyOn(AccountsController.prototype, 'getAccountByAddress');
       jest.spyOn(AccountsController.prototype, 'getSelectedAccount');
+      jest.spyOn(AccountsController.prototype, 'getAccount');
     });
 
     describe('setSelectedAccount', () => {
@@ -1981,5 +1982,30 @@ describe('AccountsController', () => {
         expect(account).toStrictEqual(mockAccount);
       });
     });
+
+    describe('getAccount', () => {
+      it('should get account by id', async () => {
+        const messenger = buildMessenger();
+
+        const accountsController = setupAccountsController({
+          initialState: {
+            internalAccounts: {
+              accounts: { [mockAccount.id]: mockAccount },
+              selectedAccount: mockAccount.id,
+            },
+          },
+          messenger,
+        });
+
+        const account = messenger.call(
+          'AccountsController:getAccount',
+          mockAccount.id,
+        );
+        expect(accountsController.getAccount).toHaveBeenCalledWith(
+          mockAccount.id,
+        );
+        expect(account).toStrictEqual(mockAccount);
+      });
+    });
   });
 });

packages/accounts-controller/src/AccountsController.ts

@@ -71,6 +71,12 @@ export type AccountsControllerGetAccountByAddressAction = {
   type: `${typeof controllerName}:getAccountByAddress`;
   handler: AccountsController['getAccountByAddress'];
 };
+
+export type AccountsControllerGetAccountAction = {
+  type: `${typeof controllerName}:getAccount`;
+  handler: AccountsController['getAccount'];
+};
+
 export type AccountsControllerActions =
   | AccountsControllerGetStateAction
   | AccountsControllerSetSelectedAccountAction
@@ -79,6 +85,7 @@ export type AccountsControllerActions =
   | AccountsControllerUpdateAccountsAction
   | AccountsControllerGetAccountByAddressAction
   | AccountsControllerGetSelectedAccountAction
+  | AccountsControllerGetAccountAction
   | KeyringControllerGetKeyringForAccountAction
   | KeyringControllerGetKeyringsByTypeAction
   | KeyringControllerGetAccountsAction;
@@ -784,5 +791,10 @@ export class AccountsController extends BaseController<
       `${controllerName}:getAccountByAddress`,
       this.getAccountByAddress.bind(this),
     );
+
+    this.messagingSystem.registerActionHandler(
+      `AccountsController:getAccount`,
+      this.getAccount.bind(this),
+    );
   }
 }