[lldb/Plugins] Add memory writing capabilities to Scripted Process

This patch adds memory writing capabilities to the Scripted Process plugin.

This allows to user to get a target address and a memory buffer on the
python scripted process implementation that the user can make processing
on before performing the actual write.

This will also be used to write trap instruction to a real process
memory to set a breakpoint.

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