[AutoTuner] Fix metadata.json regression

[luarss]

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This pull request updates the BaseAlgoEvalSmokeTest class in tools/AutoTuner/test/smoke_test_algo_eval.py to introduce the concept of a flow_variant for better configurability and reuse. The changes primarily focus on refactoring the setUp method and related commands to use this new variable.

Refactoring for flow_variant integration:

• Introduced a new class variable flow_variant with the default value "smoke-test-algo-eval" to represent the flow variant. ([tools/AutoTuner/test/smoke_test_algo_eval.pyR47-R55](diffhunk://#diff-63a772b287b174f31b4335be42c7e910f197140112906da7b1bb169517dfacf8R47-R55))
• Updated the setUp method to use flow_variant in constructing the experiment name and the reference file path, improving flexibility and consistency. ([tools/AutoTuner/test/smoke_test_algo_eval.pyR47-R55](diffhunk://#diff-63a772b287b174f31b4335be42c7e910f197140112906da7b1bb169517dfacf8R47-R55))
• Refactored the make_base method to include FLOW_VARIANT in all make commands, ensuring that the flow variant is explicitly passed to the build system. ([tools/AutoTuner/test/smoke_test_algo_eval.pyL71-R79](diffhunk://#diff-63a772b287b174f31b4335be42c7e910f197140112906da7b1bb169517dfacf8L71-R79))