feat: Adds support for the DAPR_GRPC_ENDPOINT env variable for workflows

[elena-kolevska]

Description

If the DAPR_GRPC_ENDPOINT is present and no arguments have been passed to the

Issue reference

#609

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (690ac99) 86.13% compared to head (fdfe612) 86.49%.

❗ Current head fdfe612 differs from pull request most recent head a779bab. Consider uploading reports for the commit a779bab to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #610      +/-   ##
==========================================
+ Coverage   86.13%   86.49%   +0.35%     
==========================================
  Files          74       75       +1     
  Lines        3700     3628      -72     
==========================================
- Hits         3187     3138      -49     
+ Misses        513      490      -23     

Files	Coverage Δ
ext/dapr-ext-workflow/dapr/ext/workflow/util.py	100.00% <100.00%> (ø)
ext/dapr-ext-workflow/tests/test_workflow_util.py	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes

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[berndverst]

@elena-kolevska it turns out this broke the workflow example.

[elena-kolevska]

Fixed in #632