Add windows-2025 to product build/test matrix; move tool workflows to windows-latest

[guhetier]

Adds windows-2025 alongside windows-2022 to the product code build and test matrices, and moves tool-only workflows to windows-latest so they no longer require periodic version bumps.

Supersedes #5325 (which had several bugs — see "Differences from #5325" below).

Approach

• Product code (msquic library, drivers, dotnet bindings, tests of them) — build and test on a matrix that includes both windows-2022 and windows-2025.
• Tools (non-shipped helpers — windbg ext, perf measurement infra, nuget packaging) — single windows-latest runner, no matrix.

Changes

Product matrices (added windows-2025):

• build.yml → build-windows (WinUser/UWP). Required to keep test.yml happy: test.yml already consumes windows-2025 artifacts.
• stress.yml → build-windows, stress, and recvfuzz jobs (full 2022 mirror).
• dotnet-test.yml → build-windows (both TLS) and dotnet-test (quictls, mirroring the existing 2022 pattern).

Tools (moved to windows-latest):

• plugins.yml → build_dbgext (windows-2022 → windows-latest). build_quictrace was already windows-latest.
• wan-perf.yml → wan-perf and merge-data (windows-2022 → windows-latest). build-perf was already windows-latest.
• build.yml → build-nuget (windows-2022 → windows-latest). Packaging step only — artifact name strings continue to reference windows-2022 because that's still in the build matrix.

Intentionally NOT changed

• build-windows-kernel stays on windows-2022 only — GitHub's windows-2025 image does not yet have the WDK bits to build kernel drivers (test.yml line 58 explicitly notes this, and kernel test artifacts are hardcoded to -windows-2022-).
• build-windows-official stays on windows-2022 — it's a single-target release build (-ForceOfficialRelease); OS-version compatibility is already covered by build-windows. Adding a matrix would double CI time for negligible gain.
• code-coverage.yml unchanged — preserves coverage analysis consistency.
• cargo.yml, netperf.yml, netperf-kernel-bvt.yml, check-clog.yml, check-dotnet.yml unchanged — already windows-latest.
• test.yml, test-down-level.yml already had windows-2025 in their matrices (pre-existing).

Differences from #5325

1. Drops the windows-2025 addition to build-windows-kernel in build.yml — that change would have failed because windows-2025 doesn't yet have WDK bits for driver builds.
2. Fixes -Sanitize → -SanitizeAddress typo in stress.yml 2025 entries. The original value didn't match the artifact name produced by build-reuse-win.yml, so the test jobs would not have been able to download the build output.
3. Adds the missing windows-2025 openssl entry to dotnet-test.yml's test matrix — the original PR built it but never ran the test against it.
4. Mirrors windows-2025 in stress.yml's recvfuzz job (original PR missed this — recvfuzz is a product test).
5. Fixes a latent bug in stress.yml where the stress job's artifact download name hardcoded windows-2022. Without this fix, windows-2025 matrix entries would still pull windows-2022 binaries, defeating the purpose of running them. Now uses the same conditional pattern already used by recvfuzz (uses matrix.vec.os except for WinServerPrerelease, which intentionally tests windows-2022 binaries on the prerelease OS).
6. Moves build-nuget and wan-perf.yml's merge-data job to windows-latest (original PR missed these tool runners).

Fixes #5242.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.71%. Comparing base (bcdb8c8) to head (46a3a3b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6086      +/-   ##
==========================================
- Coverage   86.11%   85.71%   -0.40%     
==========================================
  Files          60       60              
  Lines       18841    18841              
==========================================
- Hits        16225    16150      -75     
- Misses       2616     2691      +75     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.