Proposal to replace the vcpkg submodule with vcpkg manifests

This is a proposal to remove the vcpkg git submodule and satisfy its use case by adding the newer vcpkg manifest files to install/vcpkg.

Context:

• opentelemetry-cpp has a git submodule for vcpkg (at tools/vcpkg) that is used to install third-party dependencies for CI testing on Windows (via ci/setup_windows_ci_environment.ps1).
• The script installs the latest versions of the third-party dependencies available at the git tag of the vcpkg submodule (currently set to 2024.02.14).
• This submodule must be periodically updated to pull in newer versions of otel-cpp third-party dependencies and the dependency versions are not selected explicitly.
• vcpkg has added the manifest mode to explicitly select which package versions to install and this is now the recommended approach.

Proposal:

1. Clone the latest git tag for vcpkg in the CI jobs in place of the ./tools/vcpkg submodule
2. Add and use vcpkg manifest files install/vcpkg/third_party_<stable,latest>.json to install and test against specified third-party versions similar to the conan tests (see install/conan).
3. Remove the vcpkg submodule