Merge branch 'Improve error handling of verifier tests'

Florian Lehner says:

====================
These patches improve the error handling for verifier tests. With "Test
the 32bit narrow read" Krzesimir Nowak provided these patches first, but
they were never merged.
The improved error handling helps to implement and test BPF program types
that are not supported yet.

v3:
  - Add explicit fallthrough

v2:
  - Add unpriv check in error validation
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>