Run a vector truncate operation in a long loop to check timingAdd benchmarks to check runtime of truncate or zero-extend vector operations in AArch64.
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 [[ https://reviews.llvm.org/D133495 | D133495 ]], so that it can be tallied later with an alternative, more efficient code generation for the same[[ https://reviews.llvm.org/D135229 | D135229 ]] and [[ https://reviews.llvm.org/D120571 | D120571 ]].