Split arch_test.h into two files

[Alenkruth]

Split the arch_test.h into

1. arch_test_priv.h - will contain sections from the current arch_test which is required only when the test is a privileged test. These include

   • supervisor/user entry/exit macros
   • supervisor/user trap handler
   • machine trap handler
   • interrupt set/clear macros

2. arch_test_unpriv.h - will contain sections from the current arch_test which is required for normal test execution. These include

   • instruction macros
   • migration aliases

[Alenkruth]

@neelgala please check if this would work as you intended -> bd65ac0