Enable ONNX test in CI

[msaroufim]

ONNX is one of our most popular model optimization runtimes, we shouldn't disable this test in CI by default anymore, it's hiding basic failures

Our CI takes 40min and our regression tests take 1h and for context the PyTorch CI takes around 4h. Would just suggest we run regression tests on CI all the time otherwise we get dumb bugs

Fixes #2360

[codecov]

Codecov Report

Merging #2363 (d49271a) into master (8bd76ee) will increase coverage by 2.70%.
The diff coverage is 94.78%.

❗ Current head d49271a differs from pull request most recent head 951ab0a. Consider uploading reports for the commit 951ab0a to get more accurate results

@@            Coverage Diff             @@
##           master    #2363      +/-   ##
==========================================
+ Coverage   69.44%   72.15%   +2.70%     
==========================================
  Files          77       78       +1     
  Lines        3450     3641     +191     
  Branches       57       58       +1     
==========================================
+ Hits         2396     2627     +231     
+ Misses       1051     1010      -41     
- Partials        3        4       +1     

Impacted Files	Coverage Δ
ts/torch_handler/base_handler.py	55.98% <50.00%> (+0.47%)	⬆️
ts/handler_utils/micro_batching.py	90.90% <90.90%> (ø)
ts/torch_handler/request_envelope/kservev2.py	90.00% <93.75%> (ø)
...l-archiver/model_archiver/model_packaging_utils.py	92.30% <100.00%> (+32.17%)	⬆️
ts/tests/unit_tests/test_micro_batching.py	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes

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