[MicroBenchmarks] Add benchmarks to check runtime of truncate or zero-extend vector operations in AArch64

[nilanjana_basu]

Summary

This patch adds an initial set of benchmarks to check runtime of vectorized truncate or
zero-extend operations in a loop for different vector types over different vector widths.

The goal of this initial benchmark is to check the impact of D133495, D135229 and D120571.