[POC][TF FE] Support SavedModel format (with compression) (#16317)

* Added Saved Model proto descriptors

* Included Google's protobuf repository

* Added wstring version of ov::util::directory_exists

* Added initial implementation of Saved Model iterator

# Conflicts:
#	src/frontends/tensorflow/src/frontend.cpp

* Added missing proto files to repository

* Implemented reading of variables index and data files

# Conflicts:
#	src/frontends/tensorflow/src/frontend.cpp

* Renamed class

# Conflicts:
#	src/frontends/tensorflow/src/frontend.cpp

* Fix for cross-platform directory_exists

* Fixed codestyle and simplified code

* CI fixes

* Separeted Saved Model iterator from Proto iterator

* Moved variables index into separate class

* Added initial implementation of reading a variables from
saved model

# Conflicts:
#	src/frontends/tensorflow/src/frontend.cpp

* Added external variable mapping

* Code cleanup

* Commit is for discussion purposes!!!
Implemented RestoreV2 with a workaround for strings
Not optimized, includes mem leak

* In progress...

* Added DT_STRING coverage into decoder_proto

* m_variables_index moved into underlying class

* Updated copyrgihts, added space between license and code

* Moved string constant to separate class

* Added AssignVariableOp operation

* Changed behavior of RestoreV2
Updated stubs for other ops

* Second working implementation, enabled:
Program-only models
Variables reading from data files

* Extended docs

* Fixed dynamic type

* Fixed naming

* Added Snappy submodule to support compression in TF FE

* Enabled Snappy Compression for TF FE

* Make static linkage of Snappy
Changing Warning as error behavior for 3rd party

* CI fixes

* Added Snappy copyright info

* Aligned behavior of StringConstant with UnsupportedConstant

* Added correct naming and removing unused inputs/outputs

licensing/third-party-programs.txt

@@ -1547,3 +1547,61 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    See the License for the specific language governing permissions and
    limitations under the License.
 
+-------------------------------------------------------------
+
+28. Snappy (https://github.com/google/snappy/)
+
+Copyright 2011, Google Inc.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+    * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+===
+
+Some of the benchmark data in testdata/ is licensed differently:
+
+ - fireworks.jpeg is Copyright 2013 Steinar H. Gunderson, and
+   is licensed under the Creative Commons Attribution 3.0 license
+   (CC-BY-3.0). See https://creativecommons.org/licenses/by/3.0/
+   for more information.
+
+ - kppkn.gtb is taken from the Gaviota chess tablebase set, and
+   is licensed under the MIT License. See
+   https://sites.google.com/site/gaviotachessengine/Home/endgame-tablebases-1
+   for more information.
+
+ - paper-100k.pdf is an excerpt (bytes 92160 to 194560) from the paper
+   “Combinatorial Modeling of Chromatin Features Quantitatively Predicts DNA
+   Replication Timing in _Drosophila_” by Federico Comoglio and Renato Paro,
+   which is licensed under the CC-BY license. See
+   http://www.ploscompbiol.org/static/license for more ifnormation.
+
+ - alice29.txt, asyoulik.txt, plrabn12.txt and lcet10.txt are from Project
+   Gutenberg. The first three have expired copyrights and are in the public
+   domain; the latter does not have expired copyright, but is still in the
+   public domain according to the license information
+   (http://www.gutenberg.org/ebooks/53).