v8.0 module release (#22975)

https://mattermost.atlassian.net/browse/MM-52079

```release-note
We upgrade the module version to 8.0. The new module path is github.com/mattermost-server/server/v8.
```


Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

server/plugin/plugintest/mock/mock.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+// This package provides aliases for the contents of "github.com/stretchr/testify/mock". Because
+// external packages can't import our vendored dependencies, this is necessary for them to be able
+// to fully utilize the plugintest package.
+package mock
+
+import (
+	"github.com/stretchr/testify/mock"
+)
+
+const (
+	Anything = mock.Anything
+)
+
+type Arguments = mock.Arguments
+type AnythingOfTypeArgument = mock.AnythingOfTypeArgument
+type Call = mock.Call
+type Mock = mock.Mock
+type TestingT = mock.TestingT
+
+func AnythingOfType(t string) AnythingOfTypeArgument {
+	return mock.AnythingOfType(t)
+}
+
+func AssertExpectationsForObjects(t TestingT, testObjects ...any) bool {
+	return mock.AssertExpectationsForObjects(t, testObjects...)
+}
+
+func MatchedBy(fn any) any {
+	return mock.MatchedBy(fn)
+}