Dump: add output format tar and output to stdout (#10376)

* Dump: Use mholt/archive/v3 to support tar including many compressions

Signed-off-by: Philipp Homann <homann.philipp@googlemail.com>

* Dump: Allow dump output to stdout

Signed-off-by: Philipp Homann <homann.philipp@googlemail.com>

* Dump: Fixed bug present since #6677 where SessionConfig.Provider is never "file"

Signed-off-by: Philipp Homann <homann.philipp@googlemail.com>

* Dump: never pack RepoRootPath, LFS.ContentPath and LogRootPath when they are below AppDataPath

Signed-off-by: Philipp Homann <homann.philipp@googlemail.com>

* Dump: also dump LFS (fixes #10058)

Signed-off-by: Philipp Homann <homann.philipp@googlemail.com>

* Dump: never dump CustomPath if CustomPath is a subdir of or equal to AppDataPath (fixes #10365)

Signed-off-by: Philipp Homann <homann.philipp@googlemail.com>

* Use log.Info instead of fmt.Fprintf

Signed-off-by: Philipp Homann <homann.philipp@googlemail.com>

* import ordering

* make fmt

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: Matti R <matti@mdranta.net>

vendor/github.com/xi2/xz/LICENSE

@@ -0,0 +1,18 @@
+Licensing of github.com/xi2/xz
+==============================
+
+    This Go package is a modified version of
+
+        XZ Embedded  <http://tukaani.org/xz/embedded.html>
+
+    The contents of the testdata directory are modified versions of
+    the test files from
+
+        XZ Utils  <http://tukaani.org/xz/>
+
+    All the files in this package have been written by Michael Cross,
+    Lasse Collin and/or Igor PavLov. All these files have been put
+    into the public domain. You can do whatever you want with these
+    files.
+
+    This software is provided "as is", without any warranty.