Unskip sagemaker serve integration tests

[mujtaba1747]

Issue #, if available: #5802

Description of changes: Fix skipped tests in sagemaker-serve

test_model_customization_deployment.py

Problem:
cleanup_e2e_endpoints is a session-scoped fixture, but under pytest-xdist each worker gets its own session. This means multiple workers independently call Endpoint.get_all() and delete every e2e-* endpoint — including endpoints that another worker just created and is actively using.

Observed failure: Test running on worker gw2 deploys e2e-1777420521-4224, its base inference component goes InService, then a different worker's cleanup deletes it. The test on gw2 then fails when it tries to Endpoint.get() the endpoint it just created.

The teardown path had the same problem — it ran the same Endpoint.get_all() + delete loop after tests, risking a second round of collisions.

Changes:

Only delete e2e endpoints older than 24 hrs.

test_optimize_integration.py

Problem: Test kept failing because it used to run in us-east-2. And the test failed due to race condition: Other tests initializing the singleton SageMakerClient class in different region causing resource not found errors in test_optimize_integration,

Changes: Ensure tests run in a single region. Parameterized image uri in test_optimize_integration so it can run in us-west-2 and ported to other regions in future.

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