chore: Suppress xunit non-serializable data warnings

[filzrev]

This PR intended to fix issue that following xUnit warnings are recorded on test discovery.

BenchmarkDotNet.IntegrationTests: Non-serializable data ('System.Object[]') found for 'BenchmarkDotNet.IntegrationTests.ValuesReturnedByBenchmarkTest.AnyValueCanBeReturned'; falling back to single test case.

This warning is occurred when Theory data contains non serialize/deserialize data by xunit (IToolchain, Jit, and `Runtime).

It's not needed to display individual test cases on TestExplorer.
So suppress these warnings by specifing DisableDiscoveryEnumeration=true parameter.

Other changes
Add condition to reference TestAdapter project when using Release configuration only.
It's required because it failed to load BenchmarkDotNet assembly when build project with Debug configuration.
It's caused by strong-named assemblies are required to load assembly.
(These log can be confirmed by Tests log on VS output window)

[timcassell]

TestAdapter should not have to be removed in Debug configuration. We should rather fix whatever the issue is.

[filzrev]

TestAdapter should not have to be removed in Debug configuration. We should rather fix whatever the issue is.

I've removed Condition from this PR.

To fix Debug configuration issue.
It need to override common.props setting for TestAdapter project.

[timcassell]

To fix Debug configuration issue. It need to override common.props setting for TestAdapter project.

Just set <SignAssembly>false</SignAssembly> and leave a comment why, should be fine.

[filzrev]

I've removed Condition from this PR. (It's not not pushed)

Just set false and leave a comment why, should be fine.

When TestAdapter assembly is loaded by TestExplorer.
Assembly must be signed.
Without assembly signing. It failed to load assembly (It's occurred on .NET 4.6.2 target.)
Error log is recorded on output window's Tests pane.

I'll try to create another PR that enable SignAssembly for Debug build also.