[6.1] Fix code coverage job disk full

[paulmedynski]

Description

Backport of #3798 to 6.1

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 backports a fix from #3798 to the 6.1 branch to address disk space issues in code coverage jobs. The changes switch the code coverage job to use a custom 1ES image with more disk space, refactor parameter handling, add debug output for monitoring disk usage, and improve the overall structure of the code coverage template.

Key changes:

• Switched code coverage job to use ADO-MMS22-CodeCov image instead of generic Azure Pipelines image
• Refactored code coverage job template with clearer parameter structure and inline artifact downloads
• Added debug steps throughout the job to monitor disk usage and help diagnose future space issues

Reviewed changes

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

File	Description
eng/pipelines/dotnet-sqlclient-ci-core.yml	Removed unused defaultHostedPoolName variable, updated code coverage job parameters to pass image, pool, and targetFrameworks directly, and changed hardcoded pool reference from variable to string literal
eng/pipelines/common/templates/jobs/ci-code-coverage-job.yml	Comprehensive refactoring: added parameter documentation, moved artifact downloads inline, changed pool configuration to support both hosted and custom pools, added disk usage debug steps, improved cleanup logic with -ErrorAction SilentlyContinue, and changed upload condition from runtime variable to compile-time parameter

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.67%. Comparing base (b21442d) to head (0dd9a0c).
⚠️ Report is 1 commits behind head on release/6.1.

Additional details and impacted files

@@               Coverage Diff               @@
##           release/6.1    #3813      +/-   ##
===============================================
- Coverage        65.27%   63.67%   -1.61%     
===============================================
  Files              279      279              
  Lines            61765    53290    -8475     
===============================================
- Hits             40319    33932    -6387     
+ Misses           21446    19358    -2088     

Flag	Coverage Δ
addons	90.82% <ø> (ø)
netcore	67.65% <ø> (-1.66%)	⬇️
netfx	67.77% <ø> (+0.77%)	⬆️

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