Workflow logs: Add prefix to completed message

[shivamkm07]

Description

As per #7065 (comment), PR adds prefix strings to completed messages to help easier log searching.

Issue reference

Please reference the issue this PR will close: #[issue number]

Checklist

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

• Code compiles correctly
• Created/updated tests
• Unit tests passing
• End-to-end tests passing
• Extended the documentation / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#[issue number]
• Specification has been updated / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#[issue number]
• Provided sample for the feature / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#[issue number]

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (c53fc16) 62.46% compared to head (dfb897c) 62.45%.

Files	Patch %	Lines
...runtime/wfengine/backends/actors/workflow_actor.go	0.00%	2 Missing ⚠️
...runtime/wfengine/backends/actors/activity_actor.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7460      +/-   ##
==========================================
- Coverage   62.46%   62.45%   -0.02%     
==========================================
  Files         244      244              
  Lines       22132    22134       +2     
==========================================
- Hits        13825    13823       -2     
- Misses       7169     7173       +4     
  Partials     1138     1138              

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[daixiang0]

LGTM