refactor: use containerbase not buildpack terminology (#17398)

docs/usage/self-hosted-configuration.md

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

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

lib/modules/manager/composer/artifacts.spec.ts

lib/modules/manager/flux/readme.md

lib/modules/manager/gomod/artifacts.spec.ts

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

lib/modules/manager/mix/__snapshots__/artifacts.spec.ts.snap

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

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

lib/util/exec/containerbase.spec.ts

lib/util/exec/containerbase.ts

lib/util/exec/index.spec.ts

lib/util/exec/index.ts

lib/workers/global/initialize.spec.ts

lib/workers/global/initialize.ts