[6.0] Fix code coverage job disk full

[paulmedynski]

Description

Backport of #3798 to 6.0

The code coverage jobs are running out of disk space. They appear to consume upwards of 12GB of space to merge/convert 3GB of coverage logs from the various test jobs. We can diagnose why that is later. For now, I have:

• Switched the coverage job to use the ADO-MMS22-CodeCov 1ES image rather than a generic Azure Pipelines image.
  • The generic images have 14GB of disk space.
  • Our custom 1ES image has much more space.
• Removed unnecessary parameters/variables for code coverage job.
• Added debug output to help see disk usage throughout the job.

[Copilot]

Pull request overview

This PR fixes disk space issues in the code coverage job by switching to a custom 1ES image with more available disk space (ADO-MMS22-CodeCov instead of generic Azure Pipelines images). The change also refactors the code coverage job template to consolidate artifact download logic, improve parameter organization, and add debug output for disk usage monitoring.

Key Changes

• Switched code coverage job to use ADO-MMS22-CodeCov image with more disk space
• Refactored artifact download logic from caller to template, simplifying the interface
• Added disk usage debug output at multiple stages to help diagnose space issues

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
eng/pipelines/dotnet-sqlclient-ci-core.yml	Removed defaultHostedPoolName variable and refactored code coverage job parameters to pass image, pool, and targetFrameworks instead of custom download steps
eng/pipelines/common/templates/jobs/ci-code-coverage-job.yml	Complete refactor with improved documentation, consolidated artifact download logic, added disk usage debug steps, parameter type improvements, and additional cleanup steps to free disk space during processing

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.92%. Comparing base (50b1436) to head (c1ee729).
⚠️ Report is 1 commits behind head on release/6.0.

Additional details and impacted files

@@               Coverage Diff               @@
##           release/6.0    #3814      +/-   ##
===============================================
+ Coverage        75.86%   75.92%   +0.05%     
===============================================
  Files              244      244              
  Lines            40221    40221              
===============================================
+ Hits             30514    30537      +23     
+ Misses            9707     9684      -23     

Flag	Coverage Δ
addons	92.58% <ø> (ø)
netcore	75.79% <ø> (+0.05%)	⬆️

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