[lldb/Plugins] Add ScriptedProcess::GetCapabilities affordance (NFC)

This patch introduces a new method to the Scripted Process interface,
GetCapabilities.

This returns a dictionary that contains a list of flags that the
ScriptedProcess instance supports. This can be used for instance, to
force symbol lookup, when loading dynamic libraries in the scripted process.

Differential Revision: https://reviews.llvm.org/D142059



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