Add portfile changes to vcpkg such that STDLIB version can be used as described in the document

[mohnishkodnani]

Describe your environment
I am trying to use vcpkg in my project and put a dependency on opentelemetry-cpp 1.22.0
According to the document https://github.com/open-telemetry/opentelemetry-cpp/blob/main/docs/building-with-vcpkg.md
I should be able to do vcpkg install opentelemetry[stdlib]. This does not work.
as the portfile on microsoft/vcpkg does not expose stdlib yet.

I am trying this on MAC OSX.

Steps to reproduce
Add dependency in vcpkg.json

    "opentelemetry": {
      "description": "Enable OpenTelemetry backend support",
      "dependencies": [
        {
          "name": "opentelemetry-cpp",
          "version>=": "1.22.0",
          "features": ["prometheus", "otlp-grpc", "stdlib"]
        }
      ]
    }

Run
vcpkg install
Error:
error: opentelemetry-cpp@1.22.0 does not have required feature stdlib needed by metrics-library

However, the documentation says this should work.

What is the expected behavior?
What did you expect to see?
STDLIB version should be available and installable using vcpkg as mentioned in the document.

What is the actual behavior?
What did you see instead?
Error mentioned above.

Additional context
Add any other context about the problem here.
I would also like to try ABI VERSION 2 and so that should also be available as a feature on vcpkg such that ABI VERSION 2 and STDLIB combination is possible.

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