[repo] Add .NET 8 target for W3C Trace Context Integration Test in CI

[xiang17]

Towards #5799 Design discussion issue #

Changes

• Add .NET 8 in CI to run W3C Trace Context Integration Test.
• Fixed Dockerfile to build successfully by adding --break-system-packages. (mcr.microsoft.com/dotnet/sdk:net6.0 image uses Python 3.9, which doesn't have --break-system-packages option, thus adding an alternative to run without this option if it fails.)

The W3C integration test on .NET 8 has 40 failing test cases, which I asserted with Assert.StartsWith("FAILED (failures=40)", lastLine); in this PR.

Merge requirement checklist

• [x] 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)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 86.34%. Comparing base (6250307) to head (d348b4d). Report is 305 commits behind head on main.

Additional details and impacted files

[](https://app.codecov.io/gh/open-telemetry/opentelemetry-dotnet/pull/5800?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry) ```diff @@ Coverage Diff @@ ## main #5800 +/- ## ========================================== + Coverage 83.38% 86.34% +2.95% ========================================== Files 297 257 -40 Lines 12531 11150 -1381 ========================================== - Hits 10449 9627 -822 + Misses 2082 1523 -559 ``` | [Flag](https://app.codecov.io/gh/open-telemetry/opentelemetry-dotnet/pull/5800/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/open-telemetry/opentelemetry-dotnet/pull/5800/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry) | `?` | | | [unittests-Project-Experimental](https://app.codecov.io/gh/open-telemetry/opentelemetry-dotnet/pull/5800/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry) | `85.95% <ø> (?)` | | | [unittests-Project-Stable](https://app.codecov.io/gh/open-telemetry/opentelemetry-dotnet/pull/5800/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry) | `86.20% <ø> (?)` | | | [unittests-Solution](https://app.codecov.io/gh/open-telemetry/opentelemetry-dotnet/pull/5800/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry) | `86.32% <ø> (?)` | | | [unittests-UnstableCoreLibraries-Experimental](https://app.codecov.io/gh/open-telemetry/opentelemetry-dotnet/pull/5800/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry) | `85.76% <ø> (?)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry#carryforward-flags-in-the-pull-request-comment) to find out more. [see 213 files with indirect coverage changes](https://app.codecov.io/gh/open-telemetry/opentelemetry-dotnet/pull/5800/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-telemetry)