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.

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• 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?

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doc/Install_develop.rst

@@ -51,15 +51,17 @@ If you want to build or install libcaosdb without the use of Conan, feel
 free to rewrite the CMakeLists.txt as needed. The CaosDB project is open
 to merge requests which support multiple ways of installation.
 
-Building with ``vcpkg``
-~~~~~~~~~~~~~~~~~~~~~~~
+Optional: 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:
+Next to Conan, you also have the option to use the vcpkg package manager to install the
+dependencies (`vcpkg.json`). Note, however, *vcpkg is not fully supported and tested*. 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/bootstrap-vcpkg.<sh/bat> -disableMetrics
    vcpkg/vcpkg install