Update protobuf,grpc,etcd dependencies

1. Updated etcd/protobuf/grpc dependencies:

echo "
hack/pin-dependency.sh github.com/golang/protobuf latest
hack/pin-dependency.sh google.golang.org/protobuf latest
hack/pin-dependency.sh go.etcd.io/etcd/api/v3 v3.5.0-rc.0
hack/pin-dependency.sh go.etcd.io/etcd/client/v3 v3.5.0-rc.0
hack/pin-dependency.sh go.etcd.io/etcd/client/pkg/v3 v3.5.0-rc.0
hack/pin-dependency.sh go.etcd.io/etcd/pkg/v3 v3.5.0-rc.0
hack/pin-dependency.sh go.etcd.io/etcd/server/v3 v3.5.0-rc.0
hack/pin-dependency.sh go.etcd.io/etcd/tests/v3 v3.5.0-rc.0
hack/pin-dependency.sh google.golang.org/grpc latest
" | bash

2. Linted transitive dependencies until versions are clean:

hack/lint-dependencies.sh  | grep "  hack/pin-dependency.sh" | bash

3. Linted dependencies until dropped versions are clean:

hack/lint-dependencies.sh  | grep "dropreplace" | bash

4. Updated vendor and internal modules:

hack/update-vendor.sh
hack/update-internal-modules.sh

Repeated steps 2-4 until clean

vendor/go.opentelemetry.io/contrib/contrib.go

@@ -0,0 +1,28 @@
+// Copyright The OpenTelemetry 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 contrib contains common values used across all
+// instrumentation, exporter, and detector contributions.
+package contrib // import "go.opentelemetry.io/contrib"
+
+// Version is the current release version of OpenTelemetry Contrib in use.
+func Version() string {
+	return "0.20.0"
+	// This string is updated by the pre_release.sh script during release
+}
+
+// SemVersion is the semantic version to be supplied to tracer/meter creation.
+func SemVersion() string {
+	return "semver:" + Version()
+}