Add Inference Python Benchmarks Dataflow workflow

[Amar3tto]

The following jenkins job has been migrated:

https://ci-beam.apache.org/job/beam_Inference_Python_Benchmarks_Dataflow/
https://ci-beam.apache.org/job/beam_Inference_Python_Benchmarks_Dataflow_PR/

How has it been tested?

The job has been tested on Self-hosted GKE runners ubuntu 20.04.
The following test cases are passed:

• by adding a comment to the PR

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GitHub Actions Tests Status (on master branch)

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[andreydevyatkin]

LGTM

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