[native] introduce functionality for onPressRemoveKeyserver callback

Summary:
This diff introduces the user flow for when a user presses the remove keyserver button in the keyserver selection bottomsheet.

For context here are the designs for what the user flow should look like:

Linear task: https://linear.app/comm/issue/ENG-5474/introduce-onpress-remove-selected-keyserver-function

Depends on D9828

Test Plan:
Please see the demo video below

Reviewers: inka, michal, rohan

Reviewed By: inka

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9830