[CIVIS-3035] Source code tags integration

[anmarchenko]

What does this PR do?
Adds support to test.source.file and test.source.start tags that are used by source code integration to show test's source in Datadog UI:

Motivation
To achieve feature parity with other CI visibility libraries and provide basis for CODEOWNERS support.

How to test the change?
Run ruby tests from https://github.com/anmarchenko/middleman with your Datadog API key and check that source code integration works.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3688bc2) 99.22% compared to head (4b2c122) 99.23%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #95   +/-   ##
=======================================
  Coverage   99.22%   99.23%           
=======================================
  Files         142      142           
  Lines        5922     5983   +61     
  Branches      233      236    +3     
=======================================
+ Hits         5876     5937   +61     
  Misses         46       46           

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