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/boards/services/store/sqlstore/migrationstests/deleted_membership_boards_migration_test.go

@@ -6,7 +6,7 @@ package migrationstests
 import (
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 	"github.com/mgdelacroix/foundation"
 	"github.com/stretchr/testify/require"
 )

server/boards/services/store/sqlstore/migrationstests/migrate_34_test.go

@@ -6,7 +6,7 @@ package migrationstests
 import (
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 	"github.com/mgdelacroix/foundation"
 	"github.com/stretchr/testify/require"
 )

server/boards/services/store/sqlstore/migrationstests/migration35_test.go

@@ -6,7 +6,7 @@ package migrationstests
 import (
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 	"github.com/mgdelacroix/foundation"
 )
 

server/boards/services/store/sqlstore/migrationstests/migration36_test.go

@@ -6,7 +6,7 @@ package migrationstests
 import (
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 	"github.com/mgdelacroix/foundation"
 	"github.com/stretchr/testify/require"
 )

server/boards/services/store/sqlstore/migrationstests/migration37_test.go

@@ -6,7 +6,7 @@ package migrationstests
 import (
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 	"github.com/mgdelacroix/foundation"
 	"github.com/stretchr/testify/require"
 )

server/boards/services/store/sqlstore/migrationstests/migration38_test.go

@@ -6,7 +6,7 @@ package migrationstests
 import (
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 	"github.com/mgdelacroix/foundation"
 	"github.com/stretchr/testify/require"
 )

server/boards/services/store/sqlstore/migrationstests/migration_18_test.go

@@ -7,7 +7,7 @@ import (
 	"encoding/json"
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 	"github.com/mgdelacroix/foundation"
 	"github.com/stretchr/testify/require"
 )

server/boards/services/store/sqlstore/migrationstests/migration_28_test.go

@@ -6,7 +6,7 @@ package migrationstests
 import (
 	"testing"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 	"github.com/mgdelacroix/foundation"
 	"github.com/stretchr/testify/require"
 )

server/boards/services/store/sqlstore/migrationstests/migration_33_test.go

@@ -9,7 +9,7 @@ import (
 	"github.com/mgdelacroix/foundation"
 	"github.com/stretchr/testify/require"
 
-	"github.com/mattermost/mattermost-server/v6/server/boards/services/store/sqlstore"
+	"github.com/mattermost/mattermost-server/server/v8/boards/services/store/sqlstore"
 )
 
 func Test33RemoveDeletedCategoryBoards(t *testing.T) {