Removes chainconsumer and following requirements. These where causing
the CI to be very slow. Instead, rather than plotting, just list a
warning.

- Adds a tests flag for which the sampler only runs 100 steps
- Set the samples as random samples to test plotting
- Fix problems in a few of the examples

Not sure how this got undone, but this just repeats the same step of
setting the fixed_parameter properly

Minor change to how non standard parameters are checked

See merge request Monash/tupak!43

Previously, `parameters` in `fill_prior` was only ever used to fill in
the non-standard parameters if sampling in something other than the
defaults. This directy checks that. The advantage is a cleaner logic and
we no longer assume the likelihood has a
`non_standard_sampling_parameter_keys` attribute.

This reverts commit 3860e42d. Which I
mistakenly removed.

Add uniform in log prior

See merge request Monash/tupak!42