Rewrite leave session modal to the new modal component

bigbluebutton-html5/imports/locales/en.json

...button-html5/imports/ui/components/dropdown/component.jsx

...l5/imports/ui/components/leave-confirmation/component.jsx

...5/imports/ui/components/logout-confirmation/component.jsx

...tton-html5/imports/ui/components/modals-old/component.jsx

...5/imports/ui/components/modals-old/settings/component.jsx

...ml5/imports/ui/components/modals-old/settings/styles.scss

...ts/modals-old/settings/submenus/application/component.jsx

...mponents/modals-old/settings/submenus/audio/component.jsx

...omponents/modals-old/settings/submenus/base/component.jsx

...onents/modals-old/settings/submenus/session/component.jsx

...ts/ui/components/modals-old/settings/submenus/styles.scss

...mponents/modals-old/settings/submenus/users/component.jsx

...mponents/modals-old/settings/submenus/video/component.jsx

...button-html5/imports/ui/components/modals-old/styles.scss