[LAA, LV] Port to new streaming interface for opt remarks. Update LV

(Recommit after making sure IsVerbose gets properly initialized in
DiagnosticInfoOptimizationBase.  See previous commit that takes care of
this.)

OptimizationRemarkAnalysis directly takes the role of the report that is
generated by LAA.

Then we need the magic to be able to turn an LAA remark into an LV
remark.  This is done via a new OptimizationRemark ctor.

llvm-svn: 282813