fix(v-switch): add part key
fix(v-switch): add part key

Vue was reusing switch parts causing bad animation thrashing

Phlow2001/vuetify,Phlow2001/vuetify,Webifi/vuetify,vuetifyjs/vuetify,Webifi/vuetify,Phlow2001/vuetify,Phlow2001/vuetify,vuetifyjs/vuetify,Webifi/vuetify,vuetifyjs/vuetify,vuetifyjs/vuetify