[lldb/test] Fix TestAppleSimulatorOSType when multiple runtimes are installed
One can have multiple simulator runtimes installed, supporting
various generations of OSs. The logic in TestAppleSimulatorOSType
might select a rnutime older than the one targeted by the current
tools, preventing the executable from running. This commit changes
the test to look for the most recent runtime available instead.
(cherry picked from commit 977f00123a6d94c634d22356cae1da2a22f0e3df)