[OptDiag] Updating Remarks in SampleProfile

Updating remark API to newer OptimizationDiagnosticInfo API. This
allows remarks to show up in diagnostic yaml file, and enables use
of opt-viewer tool.

Hotness information for remarks (L505 and L751) do not display hotness
information, most likely due to profile information not being
propagated yet. Unsure if this is the desired outcome.

Patch by Tarun Rajendran.

Differential Revision: https://reviews.llvm.org/D36127

llvm-svn: 310763