[prometheus] Fix collection output buffer management when its resized

[jcin193]

Fixes #5661

Changes

When buffer is too small to fit its initial 85kB size its resized to fit the output, however the resized buffer is not used in final output. This ultimately results in overflow exception as cursor is correct and follows resized buffer. I also changed to use the same buffer variable for WriteTargetInfo, it also can resize the buffer.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: jcin193 (185ca98, ef1ff92, 152bd51, defdb91, 47ad841)
• ✅ login: CodeBlanch / name: Mikel Blanchard (85c61c0, 518a42f)

[Kielek]

@jcin193, could you please sign CLA? Without this your contribution cannot be accepted.

[jcin193]

Yeah, I know, unfortunately I wrote this at work, so I'll see what I can do

[github-actions]

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[jcin193]

still working on it

[jcin193]

can we get these tests running?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.17%. Comparing base (6250307) to head (518a42f).
Report is 265 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5676      +/-   ##
==========================================
+ Coverage   83.38%   86.17%   +2.79%     
==========================================
  Files         297      254      -43     
  Lines       12531    11054    -1477     
==========================================
- Hits        10449     9526     -923     
+ Misses       2082     1528     -554     

Flag	Coverage Δ
unittests	?
unittests-Project-Experimental	86.11% <100.00%> (?)
unittests-Project-Stable	86.16% <100.00%> (?)
unittests-UnstableCoreLibraries-Experimental	85.76% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...tpListener/Internal/PrometheusCollectionManager.cs	86.20% <100.00%> (+8.42%)	⬆️

... and 126 files with indirect coverage changes

[JoelDavidLang]

Thanks for this fix. 🎉 I just spent over an hour trying to find out why my metrics were broken and then finding the issue fixed by a package update, thanks to this PR. You saved me a day of frustration.