Move RunningEmptyBenchmarkTests from unit tests to integration tests #2861
Description
The unit tests (BenchmarkDotNet.Tests) are designed to be extremely fast. Currently, RunningEmptyBenchmarkTests conducts actual benchmarking, which takes too much time and hinders the quick validation of standard tests. For example, GenericTypeWithBenchmarkAttribute_RunsSuccessfully takes over 30 seconds on my machine. RunningEmptyBenchmarkTests should be moved to BenchmarkDotNet.IntegrationTests, where we keep all the longer tests.