Chore: Convert `LivechatCustomField` model to raw model (#26446)

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

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

apps/meteor/app/livechat/server/lib/Livechat.js

apps/meteor/app/livechat/server/methods/getCustomFields.js

apps/meteor/app/livechat/server/methods/registerGuest.js

apps/meteor/app/livechat/server/methods/removeCustomField.js

apps/meteor/app/livechat/server/methods/saveCustomField.js

apps/meteor/app/livechat/server/methods/saveInfo.js

apps/meteor/app/livechat/server/methods/setCustomField.js

apps/meteor/app/models/server/index.ts

apps/meteor/app/models/server/models/LivechatCustomField.js

...e/app/livechat-enterprise/server/hooks/onLoadConfigApi.js

apps/meteor/ee/app/livechat-enterprise/server/lib/Helper.js

apps/meteor/server/models/raw/LivechatCustomField.ts

...ges/model-typings/src/models/ILivechatCustomFieldModel.ts