Add TensorFlow object detection example

[yeandy]

This PR adds a TensorFlow object detection example using the MobileNet v2 320x320 model and the TensorFlow RunInference API. This is the same model that is used in the TensorRT object detection example using TensorRTRunInference API.

The goal is to be able to benchmark both implementations on DataFlow. I've added a larger dataset gs://apache-beam-ml/testing/inputs/coco_train_inputs.txt that contains 118287 examples.

Current status: I am running into an issue with signature dtypes. See #23756

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[codecov]

Codecov Report

Merging #23754 (158eda6) into master (3dd2072) will decrease coverage by 0.10%.
The diff coverage is 0.00%.

❗ Current head 158eda6 differs from pull request most recent head dbdfd2a. Consider uploading reports for the commit dbdfd2a to get more accurate results

@@            Coverage Diff             @@
##           master   #23754      +/-   ##
==========================================
- Coverage   73.23%   73.12%   -0.11%     
==========================================
  Files         719      721       +2     
  Lines       95962    96143     +181     
==========================================
+ Hits        70277    70305      +28     
- Misses      24373    24526     +153     
  Partials     1312     1312              

Flag	Coverage Δ
python	82.86% <0.00%> (-0.19%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
.../examples/inference/tensorflow_object_detection.py	0.00% <0.00%> (ø)
...python/apache_beam/io/gcp/bigquery_schema_tools.py	79.24% <0.00%> (-4.85%)	⬇️
sdks/python/apache_beam/internal/gcp/auth.py	79.16% <0.00%> (-3.70%)	⬇️
sdks/python/apache_beam/utils/interactive_utils.py	95.12% <0.00%> (-2.44%)	⬇️
...python/apache_beam/runners/worker/worker_status.py	75.33% <0.00%> (-1.34%)	⬇️
...eam/runners/portability/fn_api_runner/execution.py	92.44% <0.00%> (-0.65%)	⬇️
sdks/python/apache_beam/runners/direct/executor.py	96.46% <0.00%> (-0.55%)	⬇️
...ks/python/apache_beam/runners/worker/sdk_worker.py	89.08% <0.00%> (-0.17%)	⬇️
sdks/python/apache_beam/io/gcp/gcsio.py	92.12% <0.00%> (-0.14%)	⬇️
sdks/python/apache_beam/ml/gcp/visionml.py	92.59% <0.00%> (ø)
... and 9 more

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[github-actions]

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[github-actions]

This pull request has been closed due to lack of activity. If you think that is incorrect, or the pull request requires review, you can revive the PR at any time.