[lldb/Plugins] Enrich ScriptedThreads Stop Reasons with Exceptions

This patch adds Exceptions to the list of supported stop reasons for
Scripted Threads.

The main motivation for this is that breakpoints are triggered as a
special exception class on ARM platforms, so adding it as a stop reason
allows the ScriptedProcess to selected the ScriptedThread that stopped at
a breakpoint (or crashed :p).

rdar://87430376

Differential Revision: https://reviews.llvm.org/D117074



Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>