conformance testing: add granular violation suppressions

[lmolkova]

some instrumentations can't populate certain non-required attributes. Add mechanism allowing to suppress specific violations without turning checks off for everyone.

[Copilot]

Pull request overview

Adds a mechanism to declare and suppress specific, known Weaver live-check violations on a per-conformance-scenario basis, enabling tighter default validation while allowing instrumentations with unavoidable gaps to remain conformant.

Changes:

• Introduces ExpectedViolation and Scenario.expected_violations, and adds violation reconciliation in run_conformance.
• Tightens the span validation policy to expect server.address for more operations.
• Updates LangChain conformance scenarios to suppress the known server.address missing-attribute violation.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
util/opentelemetry-test-util-genai/src/opentelemetry/test_util_genai/conformance.py	Adds ExpectedViolation + enforcement logic so scenarios can declare and suppress specific known violations while still failing on unexpected/new ones.
policies/genai_span_validation.rego	Makes server.address an expected attribute across additional operation sets, producing stable advice IDs for suppression.
instrumentation/opentelemetry-instrumentation-genai-langchain/tests/conformance/workflow.py	Declares an expected Weaver violation for missing server.address in the workflow scenario.
instrumentation/opentelemetry-instrumentation-genai-langchain/tests/conformance/inference.py	Declares an expected Weaver violation for missing server.address in the inference scenario.
instrumentation/opentelemetry-instrumentation-genai-langchain/tests/conformance/agent.py	Declares an expected Weaver violation for missing server.address in the agent scenario.