Depends on D5115
`AddMembersList` component could be reused in another modals (i.a. in next diff - `ComposeSubchannelModal`)
Main changes:
1. split `AddMembersList` to 2 components:
- `AddMembersListContent`- contains logic responsible directly for data processing for `Members` modal
- `AddMembersList` - generate list
2. create directory for common modal components (`web/modals/components`)
3. move all associated with current `AddMembersList` components to `web/modals/components`