Vertex ai/feature store dag system test

[olayiwola-gbenga]

The create_feature_online_store task was failing because "Optimized serving" is no longer supported.

• Removed optimized serving configuration from task parameters.
• Configured Bigtable autoscaling for the Feature Online Store and added
  TriggerRule.ALL_DONE to teardown tasks to prevent leaked resources on test failure.

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Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

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