[flagd] change e2e test to use autobinding of gherkin test

[aepfli]

We currently have some e2e tests that use our test-harness repository to run standardized Gherkin tests. Sadly, this repository does not use autobinding and proper step definitions (see autobinding document). Hence, we need to implement each test case additionally.

The goal of this task is to use auto binding so our test suite will always be updated with the latest version and use the latest version for building.

• flagd e2e https://github.com/open-feature/js-sdk-contrib/tree/main/libs/providers/flagd/src/e2e
• flagd-web e2e https://github.com/open-feature/js-sdk-contrib/tree/main/libs/providers/flagd-web/src/e2e

relates to: #515

[aepfli]

@toddbaert should i duplicate this for js-sdk? i think if we do it cleverly, we can reuse the stepdefinitions for both repos