Disable tests parallelization in flaky OleDB tests

[roji]

There's reason to believe that the flakiness in #87783 is caused by concurrency issues in the ACE/Access OleDB driver being used (e.g. here). So as an easy attempt to get rid of the flakiness, I'm disabling parallelization altogether in these tests. I suggest we merge this and observe what happens in the next few days/weeks.

If this doesn't fix the flakiness, we should move away from ACE to SQL Server / LocalDB. There's a good chance we'd need to install components on the runner image though, so we'd probably want to skip the tests until that happens.

@jeffschwMSFT@jeffhandley@SamMonoRT

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[Copilot]

Pull Request Overview

This PR addresses flaky OleDB tests by disabling test parallelization to work around concurrency issues in the ACE/Access OleDB driver.

• Adds an AssemblyInfo.cs file to disable test parallelization for the OleDB test suite
• Implements a temporary workaround for known concurrency issues in the Microsoft ACE OleDB driver

[roji]

@jeffschwMSFT@jeffhandley@SamMonoRT ping - this is a tiny PR that may solve the OleDB test flakiness that's been plaguing us, would be great to get it in (I'll backport to release/10.0). If this doesn't solve the problem I'll continue to look further.

[SamMonoRT]

@jeffschwMSFT@jeffhandley@SamMonoRT ping - this is a tiny PR that may solve the OleDB test flakiness that's been plaguing us, would be great to get it in (I'll backport to release/10.0). If this doesn't solve the problem I'll continue to look further.

@roji - did we ever submit a backport PR - The RC2 window is closing, making sure we get that in time.

[roji]

@SamMonoRT nope - good point. Am noting that this is a test-only fix, but I agree it's a good idea to backport to make previous version builds more stable too.

[roji]

/backport to release/9.0-staging

[github-actions]

Started backporting to release/9.0-staging: https://github.com/dotnet/runtime/actions/runs/17666435697

[roji]

/backport to release/8.0-staging

[github-actions]

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/17666442938