test: kpv: fix tests broken by 11ef0d5

All tests for the For X Sec KPVs were broken due to additional
dependencies that broke the can_operate() test and use of an additional
function for the second argument passed to the create_kpv_* helper
functions. As a result the mock tests have had to be removed as they
currently cannot support the level of complexity introduced.
test: kpv: fix tests broken by a68e726
Prevent interpolation in some flap-related KPVs.

KPVs that have a value that should be a flap detent should not have
interpolated values when looking up based on a KTI with a floating point
index. Added support for optionally disabling interpolation in the
library routine value_at_index() and the ability to pass the flag
through to it via create_kpvs_at_ktis(). Updated with extra tests.