[lldb] Add "Trace" stop reason in Scripted Thread

This patch adds support to eStopReasonTrace to Scripted Threads.

This is necessary when using a Scrited Process with a Scripted Thread
Plan to report a special thread stop reason to the thread plan.

rdar://109425542

Differential Revision: https://reviews.llvm.org/D151043



Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>