Target .NET 8.0 for instrumentation tests

They end up getting created with whatever
preview .NET 10 version and then end up looking
for that and not finding it when running
within the .NET 8.0 job.

This should force them to build with .NET 8
and then run with .NET 8 (I think)

Author: bouwkast

tracer/test/Datadog.Trace.ClrProfiler.IntegrationTests/InstrumentationTests.cs

@@ -82,7 +82,7 @@ public async Task DoesNotInstrumentDotnetBuild()
 
             using var agent = EnvironmentHelper.GetMockAgent(useTelemetry: true);
 
-            var logDir = await RunDotnet("new console -n instrumentation_test -o . --no-restore");
+            var logDir = await RunDotnet("new console -n instrumentation_test -o . --no-restore -f net8.0");
             AssertNotInstrumented(agent, logDir);
 
             logDir = await RunDotnet("restore");
@@ -114,7 +114,7 @@ public async Task DoesNotInstrumentExcludedNames(string excludedProcess)
 
             using var agent = EnvironmentHelper.GetMockAgent(useTelemetry: true);
 
-            var logDir = await RunDotnet($"new console -n {excludedProcess} -o . --no-restore");
+            var logDir = await RunDotnet($"new console -n {excludedProcess} -o . --no-restore -f net8.0");
             AssertNotInstrumented(agent, logDir);
 
             var programCs = GetProgramCSThatMakesSpans();
@@ -152,7 +152,7 @@ public async Task DoesInstrumentAllowedProcesses(string allowedProcess)
 
             using var agent = EnvironmentHelper.GetMockAgent(useTelemetry: true);
 
-            var logDir = await RunDotnet($"new console -n {allowedProcess} -o . --no-restore");
+            var logDir = await RunDotnet($"new console -n {allowedProcess} -o . --no-restore -f net8.0");
             AssertNotInstrumented(agent, logDir);
             var programCs = GetProgramCSThatMakesSpans();
 
@@ -186,7 +186,7 @@ public async Task InstrumentsDotNetTest()
 
             using var agent = EnvironmentHelper.GetMockAgent(useTelemetry: true);
 
-            var logDir = await RunDotnet("new xunit -n instrumentation_test -o . --no-restore");
+            var logDir = await RunDotnet("new xunit -n instrumentation_test -o . --no-restore -f net8.0");
             AssertNotInstrumented(agent, logDir);
 
             // this _should_ be instrumented so we expect managed data.