Set OutputType=Exe for test projects (required by xUnit3)

[bart-vmware]

Description

The build error that apphost.exe is not found keeps popping up at corner cases, such as when running in WSL, and using .NET 10 previews. According to the xUnit documentation, setting OutputType is required. We haven't done so because it seemed redundant, but according to this comment, we should:

Executable output type is a requirement. We have been trying to set it for you via the NuGet package but the time at which it's set isn't appropriate

Quality checklist

• Your code complies with our Coding Style.
• You've updated unit and/or integration tests for your change, where applicable.
• You've updated documentation for your change, where applicable.
  If your change affects other repositories, such as Documentation, Samples and/or MainSite, add linked PRs here.
• There's an open issue for the PR that you are making. If you'd like to propose a new feature or change, please open an issue to discuss the change or find an existing issue.
• You've added required license files and/or file headers (explaining where the code came from with proper attribution), where code is copied from StackOverflow, a blog, or OSS.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Summary - All Code Coverage (ubuntu-latest)

Assembly	Line coverage	Branch coverage
Steeltoe.Bootstrap.AutoConfiguration	97.4%	100%
Steeltoe.Common	85.6%	79.8%
Steeltoe.Common.Certificates	96.2%	85.2%
Steeltoe.Common.Hosting	84%	70%
Steeltoe.Common.Http	100%	85.2%
Steeltoe.Common.Logging	81.1%	41.6%
Steeltoe.Common.Net	64.5%	66.6%
Steeltoe.Configuration.Abstractions	97.8%	92.6%
Steeltoe.Configuration.CloudFoundry	99.1%	91.6%
Steeltoe.Configuration.ConfigServer	97.2%	91.6%
Steeltoe.Configuration.Encryption	97.6%	92.4%
Steeltoe.Configuration.Kubernetes.ServiceBindings	95.1%	89.3%
Steeltoe.Configuration.Placeholder	93.8%	84.7%
Steeltoe.Configuration.RandomValue	93.2%	90%
Steeltoe.Configuration.SpringBoot	98.4%	95.4%
Steeltoe.Connectors	93.9%	89.4%
Steeltoe.Connectors.EntityFrameworkCore	81.5%	75%
Steeltoe.Discovery.Configuration	90.4%	100%
Steeltoe.Discovery.Consul	98%	94.8%
Steeltoe.Discovery.Eureka	92.7%	85.6%
Steeltoe.Discovery.HttpClients	94%	95.4%
Steeltoe.Logging.Abstractions	99.4%	96.9%
Steeltoe.Logging.DynamicConsole	100%	95.4%
Steeltoe.Logging.DynamicSerilog	99.1%	95%
Steeltoe.Management.Abstractions	100%	100%
Steeltoe.Management.Endpoint	95.5%	89.1%
Steeltoe.Management.Prometheus	95.9%	91.6%
Steeltoe.Management.Tasks	100%	****
Steeltoe.Management.Tracing	100%	75%
Steeltoe.Security.Authentication.JwtBearer	100%	100%
Steeltoe.Security.Authentication.OpenIdConnect	73.8%	59%
Steeltoe.Security.Authorization.Certificate	96.3%	75%
Steeltoe.Security.DataProtection.Redis	100%	****