ci(release): serialize tagged test projects

[ClementG91]

Summary

• serialize release test projects with MSBuild max CPU count 1
• preserve every test and its existing timeout while avoiding native Arm64 testhost starvation
• advance the immutable release version to 0.11.5 and document the non-published v0.11.4 tag

Evidence

• v0.11.4 Arm64 attempt 1: policy-store coordination hook missed its 5-second rendezvous
• v0.11.4 Arm64 attempt 2: a different FileSystemWatcher test missed its 5-second rendezvous
• both tests passed on the same SHA in PR and main native Arm64 gates
• exact serialized command passed locally: 22 projects, 1,885 tests, 0 failures