Update third party dependency management in CMake.

Rationale:

• To to give users full control over how opentelemetry-cpp satisfies its dependencies in cmake
  • For those using package managers (conan, vcpkg, ...) only use the packages installed by the manager.
  • For those wanting a single build tree use CMake's FetchContent for all dependencies.
• The CMake build does not apply a common strategy for adding third party dependencies
  • Some are submodules and added to the build tree, some require packages to be installed, and some use the ExternalProject module.
• Updating and managing what dependency versions are tested in CI is challenging.
  • The third_party_release file only accounts for some of the dependencies and the versions are not fully used in the CMake build, instead the github ci workflow files have a lot of dependency versions in them.
  • Custom bash scripts (setup_googletest.sh, setup_grpc.sh, ..) are mixed with apt installs for Linux, while vcpkg is used on Windows bringing in dependency versions from the tools/vcpkg submodule.

Goals:

• Provide new options to have otel-cpp find all dependencies as installed packages or fetch them with FetchContent
• Create a single cmake project to build/install all dependencies based on the version tags file.
• Move tested versions out of the github workflow files and test with the versions from third_party_release

Changes

• Add an otel_add_thirdparty_package function unify how third party dependencies are found/fetched.
  • Create a cmake script file for each dependency to ensure all required targets are imported/installed
  • Enable fetching from submodules or git repo with the version tags in the third_party_release.
• Fix handling of WITH_API_ONLY so it overrides any options that may import third party packages. Add api only test to verify.
• Remove the install_windows_deps CMake function and ARCH detection
  • The bootstrapping use case is addressed through fetching all dependencies with standard CMake FetchContent from github.
• Clean up cmake dependency linking
  • Use the standard CURL::libcurl target
  • Use the explicit prometheus-cpp pull and core targets
  • Use either the shared or static opentracing-cpp target
• Add cmake options to force fetch dependencies or to require all local dependencies (following the model used by Protobuf)
  • If only local dependencies should be used then set OTELCPP_THIRDPARTY_FIND_PACKAGE_ONLY=ON to prevent fetching from github or submodules.
  • If only supplying dependencies from FetchContent is desired then set OTELCPP_THIRDPARTY_FETCH_CONTENT_ONLY=ON
• Update github ci workflow to test fetching all dependencies from github (no git submodules).
• Add a cmake project to build/install all dependencies based on the selected git tag file.
  • Remove the googletest, abseil, protobuf, and grpc install scripts and replace with a single install_thirdparty script.
• Add the ms-gsl dependency to the vcpkg setup ci script and fix the api cmake file so the component will find this dependency if WITH_GSL=ON

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed