[wasm] Use correct current runtime pack version for Wasm.Build.Tests

[maraf]

Wasm.Build.Tests are not a shipping project, PackageVersion will have a version suffix even for release branch, where actual runtime pack version doesn't have version suffix. Use ProductVersion in that case, based on StabilizePackageVersion value.

Fixes https://github.com/dotnet/runtime/issues/109626 Fixes https://github.com/dotnet/runtime/issues/108937 Fixes https://github.com/dotnet/runtime/issues/108938

[dotnet-policy-service[bot]]

Tagging subscribers to this area: @akoeplinger, @matouskozak See info in area-owners.md if you want to be subscribed.

[lewing]

tell-mode test change