SBDebugger::SetInputFile, SetOutputFile, etc.

Summary:
Add new methods to SBDebugger to set IO files as SBFiles instead of
as FILE* streams.

In future commits, the FILE* methods will be deprecated and these
will become the primary way to set the debugger I/O streams.

Reviewers: JDevlieghere, jasonmolenda, labath

Reviewed By: labath

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D68181