User is able to leave an organization
## Problem
Users can be [removed](https://gitlab.com/gitlab-org/gitlab/-/issues/435931 "Removing the organization user from the organization") from Organizations. Similarly, they should have a right to leave an Organization.
## Proposal
- Add an option to `Leave Organization`. Where should this be located?
- Leaving an Organization should remove a user as a member from all the groups and projects contained by the Organization.
- User is warned about the consequences of leaving the Organization.
- The user account stays intact.
- As a result of leaving, the user loses member privileges for all the groups and projects contained in the Organization.
- If the user is a member of more than 1 Organization, the Organization that the user left will not be available in the Organization switcher any longer.
- If the user is a member of only 1 Organization and leaves that Organization, they are added to the default Organization instead.
Add ellipse menu to organization homepage
Clicking the ellipse opens a menu with an option to leave the organization
{width="309" height="143"}
Clicking `Leave organization` opens a confirmation modal
{width="613" height="232"}
If the user is the sole owner of a group prevent leaving and display the following modal
{width=615 height=194}
If the user is the sole owner of an organization prevent leaving and display the following modal
<details>
<summary>
Future iteration
</summary>
</details>
### Implementation plan
1. Add leave action to `app/assets/javascripts/vue_shared/components/list_actions/constants.js`
2. Render `app/assets/javascripts/vue_shared/components/list_actions/list_actions.vue` in `app/assets/javascripts/organizations/users/components/users_view.vue` by using the `user-actions` slot in `<users-table>`
3. Add `action: this.onActionLeave` and `text: `Leave organization` to leave action and then pass to `actions` prop
4. In `onActionLeave` open a `GlModal`
4. Check permissions added in https://gitlab.com/gitlab-org/gitlab/-/issues/441577 to determine what the modal should say.
5. If user confirms use GraphQL Mutation in https://gitlab.com/gitlab-org/gitlab/-/issues/423005 to remove the organization user
issue