Add vcpkg support

Summary

While exploring vcpkg I realized that with Conan 2 it should be possible to actually offer both Conan and vcpkg as package managers. This MR brings support for compilation with vcpkg to the cpplib.

Related to #81 (closed)

Focus

• A few files were added to support vcpkg, and some changes had to be made to the CMakeLists.txt file to make it compatible with both Conan 2 and vcpkg.
• Instructions on how to build with vcpkg can be found in docs/Install_develop.rst.
• A GitLab CI step to test building with vcpkg was added to the pipeline.

Test Environment

Follow new build instructions to test vcpkg.

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• All automated tests pass
• Reference related issues
• Up-to-date CHANGELOG.md (or not necessary)
• Up-to-date JSON schema (or not necessary)
• Appropriate user and developer documentation (or not necessary)
  • How do I use the software? Assume "stupid" users.
  • How do I develop or debug the software? Assume novice developers.
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• Appropriate user and developer documentation (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

For further good practices have a look at our review guidelines.

doc/Install_develop.rst

@@ -19,6 +19,34 @@ which have ``make`` installed, type this in your command line terminal:
 
    make conan
 
+Building with ``vcpkg``
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Instead of Conan, you can use the vcpkg package manager to install the dependencies (`vcpkg.json`). It's included as 
+a submodule in the project. To install the dependencies, run the following commands:
+
+.. code:: console
+
+   ./vcpkg/bootstrap-vcpkg.<sh/bat>
+   vcpkg/vcpkg install
+
+
+Copy the ``grpc-cpp-plugin`` to the build directory (TODO: This should ideally be done automatically by CMake): 
+
+.. code:: console
+
+   mkdir -p build/build_tools
+   cp vcpkg_installed/<os>/tools/grpc/grpc_cpp_plugin build/build_tools
+
+Then compile the project with CMake by including the vcpkg toolchain file:
+
+.. code:: console
+
+   cd build
+   cmake -S .. -B . -DCMAKE_TOOLCHAIN_FILE=../vcpkg/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-linux -DCMAKE_BUILD_TYPE=Release
+   cmake --build .
+
+
 Manual build
 ~~~~~~~~~~~~
 
@@ -28,7 +56,7 @@ package manager. The compiler must support the C++17 standard.
 1. clone/update the subrepo ``git submodule update --init proto``
 2. ``conan install . -s build_type=Release --build=missing``
 3. ``cd build/Release``
-4. ``cmake .``
+4. ``cmake -S ../.. -G "Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=generators/conan_toolchain.cmake  -DCMAKE_POLICY_DEFAULT_CMP0091=NEW -DCMAKE_BUILD_TYPE=Release``
 5. ``cmake --build .``
 
 You may also want to install libcaosdb system-wide to
@@ -74,7 +102,7 @@ as compiler. We use `cmake <https://cmake.org/download/>`__ as build
 tool.
 
 1. clone/update the subrepo ``git submodule update --init proto``
-2. ``conan install .. -g visual_studio -s arch=x86_64 -s build_type=Release -s compiler.toolset=v142 -s compiler.version=16 -s compiler.runtime=MD --build=missing --update``
+2. :code:``conan install .. -g visual_studio -s arch=x86_64 -s build_type=Release -s compiler.toolset=v142 -s compiler.version=16 -s compiler.runtime=MD --build=missing --update``
 3. ``cd build/Release``
 5. ``cmake -B . ..``
 6. open ``libcaosdb.sln`` with Visual Studio, change the buildtype to