Add a performance test specific to parallel downloadsThis commit introduces a performance test measuring the impact of parallel downloads:- parallel download of artifacts- parallel download of metadataThe test project is a Spring Boot app (copied from their samples), and we're using a remote repository testfixture to simulate network latency.
Fix no-daemon performance testsPass the jvm args to the client VM, so Gradle isn't forced to starta single-use daemon.Adds a test for a cold daemon, but without recompling scripts, i.e.what a developer usually experiences in the morning when they turnon their laptop.
Redirect output of performance tests to diskThe performance tests now no longer use our integration test fixtures.Instead they use a simple ProcessBuilder to be closer to what a userwould do. More specifically, we no longer capture output in the test VM,as that can introduce its own flakiness into the measurement. It alsoreduces the memory needed to run the performance tests. Last but not leastspooling the output to disk makes later analysis easier.