Add initial E2E test framework for opal-server

[SiddaAbhishek]

Fixes #677

What was added

• Introduced E2E test framework for opal-server using PyTest
• Added initial healthcheck E2E test that starts the real server and validates HTTP response

How to test

1. Create virtualenv with Python 3.11
2. Install requirements
3. Run: pytest packages/opal-server/opal_server/tests

[netlify]

✅ Deploy Preview for opal-docs canceled.

Name	Link
🔨 Latest commit	7ec7b62
🔍 Latest deploy log	https://app.netlify.com/projects/opal-docs/deploys/6960e60e99b255000803ea47

[SiddaAbhishek]

I’ve added an initial E2E test framework for opal-server using PyTest.
A demo pictures showing the test setup and successful run is

[SiddaAbhishek]

Added a follow-up commit to stabilize the E2E suite based on real Docker runtime behavior.

Specifically:

• Filtered known non-fatal Datadog connection errors from log validation
• Relaxed OPA data assertion to account for valid empty data responses during initial sync

All tests now pass reliably via make e2e-test.