[flagd] Add additional e2e tests for in-process provider

[toddbaert]

With the completion of https://github.com/open-feature/js-sdk-contrib/pull/633, we should add additional e2e tests in the flagd provider.

We should:

• run the evaluation suite an additional time (using the in-process provider)
• run the additional flagd.feature for both in-process and RPC providers
• run the additional flagd-json-evaluation.feature for just the in-process provider (no need to test this logic in RPC, it's built into flagd)
• run the sync testbed in the CI (see equivalent in Java: https://github.com/open-feature/java-sdk-contrib/blob/main/.github/workflows/ci.yml#L15C1-L24).

See similar in Java provider: https://github.com/open-feature/java-sdk-contrib/tree/main/providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/e2e