Migrate Role Dropdown to GlCollapsibleListbox

What does this MR do and why?

Migrate GlDropdown to GlCollapsibleListbox on app/assets/javascripts/members/components/table/role_dropdown.vue

Changelog: changed

Screenshots or screen recordings

Before	After
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How to setup and validate locally

1. Open any project and go to Manage > Members (e.g. /flightjs/Flights/-/project_members)
2. To show the ldap option, remove v-if from <ldap-dropdown-item/> on line 118.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #413441 (closed)