[XLA:MSA] Add a new function to estimate the total trip counts of instructions.
[XLA:MSA] Add a new function to estimate the total trip counts of instructions.

The current trip count calculation is based on ```GetWhileNestMultiplier```, which assumes all layers of nested loops have the same trip count. Instead, the new function ```CalculateComputationNestTripCount``` uses the ```ComputeWhileLoopTripCount``` to get the estimated trip count for each individual while loop, which is expected to make more accurate trip count estimation.
