[core][aDAG] Fix microbenchmark regression adag 2

[rkooo567]

Why are these changes needed?

After multi ref PR, we cannot just do await on returned value when it is multi ref output

Related issue number

Closes #47667

Checks

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    method in Tune, I've added it in doc/source/tune/api/ under the
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• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[kevin85421]

Is this related to #47667? If so, add "closes #47667" in the PR description.