Refactor timeout scaling factor initialization In order to stabilize tests on (heavily loaded) CI infrastructure, reasses scaling factor every three minutes. Also include (simple) I/O benchmark to compensate for (overloaded) I/O subsystem of CI slaves. For details, see `Builder::TestReport::Result >> timeoutScale`

..\..\..\projects\smalltalk\stx -I --noInfoPrint --noBanner --abortOnInternalError --abortOnMessageSendError --ignoreHalt --execute SelfTest.st