Merge branch v2.8 into v2.9

CHANGELOG.md

docs/content/providers/docker.md

docs/content/providers/ecs.md

docs/content/providers/kubernetes-ingress.md

docs/content/reference/static-configuration/cli-ref.md

docs/content/reference/static-configuration/env-ref.md

go.mod

go.sum

integration/helloworld/helloworld.pb.go

pkg/provider/docker/docker.go

script/gcg/traefik-bugfix.toml