Security dashboard shows a count of 100 projects even if there are more

On the security dashboard, a project count is shown for each grade. However, if there are more than 100 projects, "100" is incorrectly shown for the count:

Due to a limitation with the backend only returning the first 100 projects for each grade, if there are more than 100 projects, we need to show "100+". While we could show the actual count, the list will only have the first 100, so to avoid confusion we will show "100+" instead of the actual count. If there are 100 projects or less, we will show the actual count.

Implementation Plan

• Add count property to ee/app/assets/javascripts/security_dashboard/graphql/queries/group_vulnerability_grades.query.graphql
• Add count property to ee/app/assets/javascripts/security_dashboard/graphql/queries/instance_vulnerability_grades.query.graphql
• Modify ee/app/assets/javascripts/security_dashboard/components/shared/project_security_status_chart.vue to show the actual project count if count is <= 100, or "100+" if it's more