feat: Allow admins to control if visitors can close omnichannel conversations (#33139)

.changeset/healthy-rivers-nail.md

apps/meteor/app/livechat/imports/server/rest/appearance.ts

apps/meteor/app/livechat/server/api/lib/appearance.ts

apps/meteor/app/livechat/server/api/lib/livechat.ts

apps/meteor/app/livechat/server/api/v1/room.ts

apps/meteor/app/livechat/server/lib/LivechatTyped.ts

...or/client/views/omnichannel/appearance/AppearanceForm.tsx

...or/client/views/omnichannel/appearance/AppearancePage.tsx

apps/meteor/server/settings/omnichannel.ts

...meteor/tests/e2e/omnichannel/omnichannel-livechat.spec.ts

apps/meteor/tests/end-to-end/api/livechat/00-rooms.ts

packages/i18n/src/locales/en.i18n.json

packages/livechat/src/routes/Chat/connector.tsx

packages/livechat/src/routes/Chat/container.js

packages/livechat/src/store/index.tsx