replace reference/docker for github.com/distribution/reference v0.5.0

The reference/docker package was a fork of github.com/distribution/distribution,
which could not easily be used as a direct dependency, as it brought many other
dependencies with it.

The "reference' package has now moved to a separate repository, which means
we can replace the local fork, and use the upstream implementation again.

The new module was extracted from the distribution repository at commit:
b9b19409cf

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

reference/docker/regexp_deprecated.go

@@ -0,0 +1,66 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package docker
+
+import (
+	"github.com/distribution/reference"
+)
+
+// DigestRegexp matches well-formed digests, including algorithm (e.g. "sha256:<encoded>").
+//
+// Deprecated: use [reference.DigestRegexp].
+var DigestRegexp = reference.DigestRegexp
+
+// DomainRegexp matches hostname or IP-addresses, optionally including a port
+// number. It defines the structure of potential domain components that may be
+// part of image names. This is purposely a subset of what is allowed by DNS to
+// ensure backwards compatibility with Docker image names. It may be a subset of
+// DNS domain name, an IPv4 address in decimal format, or an IPv6 address between
+// square brackets (excluding zone identifiers as defined by [RFC 6874] or special
+// addresses such as IPv4-Mapped).
+//
+// Deprecated: use [reference.DomainRegexp].
+//
+// [RFC 6874]: https://www.rfc-editor.org/rfc/rfc6874.
+var DomainRegexp = reference.DigestRegexp
+
+// IdentifierRegexp is the format for string identifier used as a
+// content addressable identifier using sha256. These identifiers
+// are like digests without the algorithm, since sha256 is used.
+//
+// Deprecated: use [reference.IdentifierRegexp].
+var IdentifierRegexp = reference.IdentifierRegexp
+
+// NameRegexp is the format for the name component of references, including
+// an optional domain and port, but without tag or digest suffix.
+//
+// Deprecated: use [reference.NameRegexp].
+var NameRegexp = reference.NameRegexp
+
+// ReferenceRegexp is the full supported format of a reference. The regexp
+// is anchored and has capturing groups for name, tag, and digest
+// components.
+//
+// Deprecated: use [reference.ReferenceRegexp].
+var ReferenceRegexp = reference.ReferenceRegexp
+
+// TagRegexp matches valid tag names. From [docker/docker:graph/tags.go].
+//
+// Deprecated: use [reference.TagRegexp].
+//
+// [docker/docker:graph/tags.go]: https://github.com/moby/moby/blob/v1.6.0/graph/tags.go#L26-L28
+var TagRegexp = reference.TagRegexp