It's necessary to make this clamping there so that returned values are
always used consistently in taskmgr, including in places where the
values are directly fetched into other functions.
This is a free adaptation from
Wine commit
a9742b3210c4cec67aca3c0012f3b9504a4368cf
From: Gerald Pfeifer <gerald@pfeifer.com>
taskmgr: Move out-of-domain checking into
PerfDataGetProcessorUsage() and PerfDataGetProcessorSystemUsage().
The CMD_LINE_CACHE index (idx) does not update when programs are closed.
Compare it with the process id (pid) in the cache and determine the pid
by the index in the same cache.
CORE-17115
