Expose vulnerabilities by age in Project Security Dashboard

Why are we doing this work?

In order to allow teams to identify vulnerabilities that may be slipping past their SLAs we need to expose vulnerabilities by age in the Project's Security Dashboard

Design issue: #234193

Implementation plan

• backend Create Types::VulnerabilitiesCountByAge (ee/app/graphql/ee/types/vulnerabilities_count_by_age_type.rb)
• backend Create Resolvers::VulnerabilitiesCountByAgeResolver (ee/app/graphql/resolvers/vulnerabilities_count_by_age_resolver.rb)
• backend Expose :vulnerabilities_count_by_age in EE::Types::Project (ee/app/graphql/ee/types/project_type.rb)