Update flagd RPC and OFREP to support metadata

[toddbaert]

With this schema change, flag metadata can now be stored in flag configuration files. Specifically, these can contain things like version and flag set id information so that consumers can use this data in flag evaluations, caching, telemetry etc.

We need to add this metadata into flags which are evaluated in RPC mode as well as in OFREP. That means modifications to the handlers here and here, respectively. Essentially, we need to take the properties from the flag definition and include them in the response in the flag metadata field.

Acceptance criteria:

• update schema git submodule to use changes in feat: add flag set and flag metadata to schema flagd-schemas#173
• OFREP handler adds flag id and version metadata (https://github.com/open-feature/flagd/blob/main/flagd/pkg/service/flag-evaluation/ofrep/handler.go)
• RPC evaluations add flag id and version metadata (https://github.com/open-feature/flagd/blob/main/flagd/pkg/service/flag-evaluation/flag_evaluator_v2.go)
• associated tests for the 2 handlers above

[aasifkhan7]

I'd like to work on this one @toddbaert ! Could you please assign it to me?

[aepfli]

i assigned you @aasifkhan7, if you need help, feel free to reach out to us.

[aasifkhan7]

This is the initial draft of the PR: #1476.

@aepfli @toddbaert @beeme1mr Could you please take a look and let me know if I'm on the right track, or if I'm off course? I'll continue refining the PR in subsequent iterations.