[lldb/Utility] Add GetDescription(Stream&) to StructureData::*

This patch improves the StructuredData classes to provide a
GetDescription(lldb_private::Stream&) affordance.

This is very convenient compared to the Dump method because this try to
pretty print the structure instead of just serializing it into a JSON.

This patch also updates some parts of lldb (i.e. extended crash info) to
use this new affordance instead of StructuredData::Dump.

Differential Revision: https://reviews.llvm.org/D135547



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