Enhancement

Provide a library to override performance-critical routines for aarch64 targets.
The implementations are imported from official ARM repo.
To reduce dispatching cost, indirect function technique is utilized. Therefore,
this library should only be enabled with ELF targets.

Considerations:

• By Jun, 2022, most enterprise OSs (CentOS 7, CentOS Stream 8 and RHEL 8) still
  use relatively old glibc on ARM64, where ASIMD, MTE, DC ZVA and SVE are not
  fully utilized. However, it is becoming increasingly common to use ARM64 instances
  in cloud-native situations.
• optimized-routines repo is actively maintained by ARM officials. Therefore,
  the qualities can be ensured while using it also enables us to keep sync with latest
  acceleration techniques.