feat: admin config init (#8546)

lib/config/admin.ts

lib/config/common.ts

lib/config/definitions.ts

lib/manager/bundler/__snapshots__/artifacts.spec.ts.snap

lib/manager/bundler/artifacts.spec.ts

lib/manager/cargo/__snapshots__/artifacts.spec.ts.snap

lib/manager/cargo/artifacts.spec.ts

lib/manager/cocoapods/__snapshots__/artifacts.spec.ts.snap

lib/manager/cocoapods/artifacts.spec.ts

lib/manager/common.ts

lib/manager/composer/__snapshots__/artifacts.spec.ts.snap

lib/manager/composer/artifacts.spec.ts

lib/manager/gomod/__snapshots__/artifacts.spec.ts.snap

lib/manager/gomod/artifacts.spec.ts

lib/manager/helmv3/__snapshots__/artifacts.spec.ts.snap

lib/manager/helmv3/artifacts.spec.ts

lib/manager/nuget/__snapshots__/artifacts.spec.ts.snap

lib/manager/nuget/artifacts.spec.ts

lib/manager/pipenv/__snapshots__/artifacts.spec.ts.snap

lib/manager/pipenv/artifacts.spec.ts