Unify executorch_runner app to handle all types of ptes

[digantdesai]

          sure we can clean it up in the next PR

Originally posted by @digantdesai in #659 (comment)

[digantdesai]

Couple of more issues which we deferred in #659, making a list here so we don't forget,

• Some tabs literals in following,
  • fbcode/executorch/backends/arm/cmake/build.sh:19
  • fbcode/executorch/examples/arm/run.sh:50
  • fbcode/executorch/examples/arm/setup.sh:47
• remove build.sh and toolchain.sh - use setup.sh and run.sh
• Align example script with xnnpack setup - removing minimal.py

@robell - let me know if you want to split these and I can also help with these things, so we can close this on Mon.