refactor(test): Load fixtures with helpers (#9699)

lib/config/decrypt.spec.ts

lib/config/presets/index.spec.ts

lib/datasource/cdnjs/index.spec.ts

lib/datasource/crate/index.spec.ts

lib/datasource/dart/index.spec.ts

lib/datasource/galaxy-collection/index.spec.ts

lib/datasource/galaxy/index.spec.ts

lib/datasource/git-refs/index.spec.ts

lib/datasource/git-tags/index.spec.ts

lib/datasource/gradle-version/index.spec.ts

lib/datasource/helm/index.spec.ts

lib/datasource/hex/index.spec.ts

lib/datasource/jenkins-plugins/index.spec.ts

lib/datasource/maven/index.spec.ts

lib/datasource/nuget/index.spec.ts

lib/datasource/packagist/index.spec.ts

lib/datasource/pypi/index.spec.ts

lib/datasource/repology/index.spec.ts

lib/datasource/ruby-version/index.spec.ts

lib/datasource/rubygems/__fixtures__/rubygems-org.txt