[unittest] Parallelize UnitTestSuite (#319)

* [unittest] Parallelize UnitTestSuite so all tests have their own timer, runs until all finish or any timeout. Adds SimpleTimer.

* [util] Timer spacing cleanup

* [unittest] Remove Config reference to UnitTestTimeout

src/main/scala/uncore/tilelink2/Fuzzer.scala

@@ -254,7 +254,7 @@ class TLFuzzRAM extends LazyModule
   }
 }
 
-class TLFuzzRAMTest extends UnitTest {
+class TLFuzzRAMTest extends UnitTest(500000) {
   val dut = Module(LazyModule(new TLFuzzRAM).module)
   io.finished := dut.io.finished
 }