[IMPROVE] Refactor Omnichannel Past Chats List (#17346)

* Add all the features

* css improved

* changed some css

* Code and CSS Improvement

* Code and CSS Improvement

* some changes

* changes made

* Api modified

* css changes with Api modification

* chnages made on 28April

* changes made on 1may

* changes made on 6th may

* css chang

* css chang

* css chang

* css chang

* css chang

* css chang

* css chang

* changes made on 7th may

* Update visitors.js

* Fix indentations.

* Fix css/style issues.

* Refactored the codebase.

* Fix unused imports.

* Fix CSS file.

* Add new query to fetch chat history.

* Remove unnecessary console log.

* UI-UX improvements.

* Fix Css stuff.

* Fix fetch data.

* Remove unnecessary helper method.

* Final version.

* Fix empty-line missing.

* Additional improvements.

Co-authored-by: Renato Becker <renato.augusto.becker@gmail.com>