Move C++ supportlib code #2596
Description
We should move some files, functions and classes for more consistent categorization.
- RandomGenerator -> Utils
- StaticString -> MemoryKit
- DynamicBuffer -> MemoryKit
- FdGuard -> IOUtils (Move FdGuard to IOUtils and improve it #2607)
- StdioGuard -> IOUtils
- BackgroundEventLoop -> Utils
- FileDescriptor -> IOUtils
- FastStringStream -> StrIntUtils
- CachedFileStat -> FileTools
- SafeLibev -> ServerKit
- getSystemTempDir, parseModeString, getSignalName -> SystemTools
- escapeForXml -> StrIntUtils
- Get rid of ClassUtils, only used by WatchdogLauncher.
- Get rid of SpeedMeter, only used by SystemMetricsCollector for collecting fork rate and swap rate. Nowadays everybody has a monitoring system so the utility of fork rate and swap rate collection is dubious, so we can get rid of them.