[NEW] Capability to search visitors by custom fields (#26312)

apps/meteor/app/livechat/imports/server/rest/visitors.js

apps/meteor/app/livechat/server/api/lib/rooms.js

apps/meteor/app/livechat/server/api/lib/visitors.js

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

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

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

...client/views/omnichannel/customFields/CustomFieldsForm.js

...lient/views/omnichannel/customFields/CustomFieldsRoute.js

...nt/views/omnichannel/customFields/EditCustomFieldsPage.js

...ent/views/omnichannel/customFields/NewCustomFieldsPage.js

apps/meteor/packages/rocketchat-i18n/i18n/en.i18n.json

apps/meteor/packages/rocketchat-i18n/i18n/pt-BR.i18n.json

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

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

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

apps/meteor/tests/data/livechat/custom-fields.ts

apps/meteor/tests/end-to-end/api/livechat/09-visitors.ts

packages/core-typings/src/ILivechatCustomField.ts

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

packages/model-typings/src/models/ILivechatVisitorsModel.ts