[VSA] Add option to clear all projects in group-level VSA

Summary

The project selector/dropdown in group-level VSA supports multi selection. However, it doesn't allow users to unselect all previously selected projects, i.e., users would need to unselect each project individually.

Related to #336385 (closed)

Proposal

• Let's add a Clear all link to the dropdown, preferably at the top of the dropdown.

Possible fixes