tests: fix security-seccomp test by skip using the apparmor parser with cache (#12893)
The test is failing sporadically in uc18. The error seems to be related
to the apparmor_parser which is generating incorrect definitions. This
error seems to be caused because of cached profiles.
interfaces: update comments about `no-expr-simplify`
This commit is a followup for the comments in the review for
PR#12918 [1]. As snapd is no longer using `no-expr-simplify`
all reference in the code got updated.
The `AddParametricSnippet()` that was originally introduced to
avoid exponential memory growth with the parser is still useful
and needed because the measurements in PR#12943 show that
multiple lines with overlaping patterns will slow down the
apparmor_parser when running with default `expr-simplify`.
The comments are updated accordingly in this commit.