libsel4bench: Support dangerous MSR interface

Uses the dangerous MSR interface if it's enabled instead of DebugRun

libsel4bench: Use kernel exported PMC

Fix all the whitespace

- remove trailing whitespace
- remove duplicate blank lines
- remove blank lines at end of files

Fix licenses

sel4bench: style

sel4bench: use ccnt_t and remove duplicate

Was duplicated sel4bench_counter_t and format function

sel4bench: improve interface

- define array of generic events
- drop generic events that don't exist for all platforms (i.e are not
generic)
- define number of generic events
- define types to illustate the difference between a counter and an
event

sel4bench: remove layer of indirection in events

No longer required now directory structure is fixed.

sel4bench: use #pragma once

sel4bench: fix include structure and licenses

For too long sel4bench has relied on relative includes
and filenames with the CPU/ARMV in it.

Finally fix it.