feat: show all accounts in VS Code accounts view

Description

This MR changes the authentication provider so that we can provide VS Code with all extension accounts (in all instances, both OAuth and PAT).

This MR also adds reactivity, so that when you sign out, the account gets removed from the list.

before	after
Only OAuth token is shown for gitlab.com	All GitLab accounts are shown

Also, the sign-out command did not update the list of accounts. I.e. signing out didn't remove the account from the list of accounts

before	after
sign-out-not-working	sign-out-working

In the same way, authenticating using OAuth didn't add the account to the list. (The list was only updated once the extension started.)

Related Issues

Resolves #1381 (closed)

How has this been tested?

1. Add OAuht and PAT accounts to the extension (using the Gitlab: Authenticate command)
2. see that both accounts are in the account menu (see screencasts and screenshots above
3. validate that when you sign out from the account, it disappears from the list

What CHANGELOG entry will this MR create?

• fix: Bug fix fixes - a user-facing issue in production - included in changelog
• feature: New feature - a user-facing change which adds functionality - included in changelog
• BREAKING CHANGE: (fix or feature that would cause existing functionality to change) - should bump major version, mentioned in the changelog
• None - other non-user-facing changes

src/desktop/accounts/oauth/gitlab_authentication_provider.ts

 import vscode from 'vscode';
+import { differenceBy } from 'lodash';
 import { accountService, AccountService } from '../account_service';
 import { Account } from '../../../common/platform/gitlab_account';
 
@@ -13,10 +14,8 @@ const convertAccountToSession = (account: Account): vscode.AuthenticationSession
 });
 
 const makeDiff = (prev: Account[], next: Account[]) => {
-  const prevIds = prev.map(a => a.id);
-  const nextIds = next.map(a => a.id);
-  const added = next.filter(a => !prevIds.includes(a.id)).map(convertAccountToSession);
-  const removed = prev.filter(a => !nextIds.includes(a.id)).map(convertAccountToSession);
+  const added = differenceBy(next, prev, a => a.id).map(convertAccountToSession);
+  const removed = differenceBy(prev, next, a => a.id).map(convertAccountToSession);
   return { added, removed, changed: undefined };
 };