[mlgo] Incrementally update FunctionPropertiesInfo during inlining

Re-computing FunctionPropertiesInfo after each inlining may be very time
consuming: in certain cases, e.g. large caller with lots of callsites,
and when the overall IR doesn't increase (thus not tripping a size bloat
threshold).

This patch addresses this by incrementally updating
FunctionPropertiesInfo.

Differential Revision: https://reviews.llvm.org/D125841