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/components/common_counter.js

@@ -25,7 +25,7 @@ export function counterRenderer(counterType, isBold = true) {
     return (displayNumber, pluralReady) => (
       <FormattedMessage
         id='account.statuses_counter'
-        defaultMessage='{count, plural, one {{counter} Toot} other {{counter} Toots}}'
+        defaultMessage='{count, plural, one {{counter} Post} other {{counter} Posts}}'
         values={{
           count: pluralReady,
           counter: renderCounter(displayNumber),