Change "Direct" status visibility to "Only people I mention" in web UI (#18146)

- Change name of conversations column in web UI
- Change hotkey for opening conversations column from `g d` to `g c` in web UI
- Remove shortcuts for creating direct-visibility statuses from web UI

app/javascript/mastodon/features/directory/components/account_card.js

@@ -191,7 +191,7 @@ class AccountCard extends ImmutablePureComponent {
             <div className='account-card__counters__item'>
               <ShortNumber value={account.get('statuses_count')} />
               <small>
-                <FormattedMessage id='account.posts' defaultMessage='Toots' />
+                <FormattedMessage id='account.posts' defaultMessage='Posts' />
               </small>
             </div>