Update to use "time" not "step" in dust 0.12.x

[richfitz]

Fairly robotic, but also fairly painful. Once this is passing there are a couple of rough edges that can be smoothed over as this package was already having a bit of a fight with both step and time being used

[codecov]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage 👍

Coverage data is based on head (a1134f0) compared to base (802ae3c).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #222   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           29        29           
  Lines         2851      2834   -17     
=========================================
- Hits          2851      2834   -17     

Impacted Files	Coverage Δ
R/deterministic.R	100.00% <100.00%> (ø)
R/deterministic_state.R	100.00% <100.00%> (ø)
R/if2.R	100.00% <100.00%> (ø)
R/particle_filter.R	100.00% <100.00%> (ø)
R/particle_filter_data.R	100.00% <100.00%> (ø)
R/particle_filter_multistage.R	100.00% <100.00%> (ø)
R/particle_filter_state.R	100.00% <100.00%> (ø)
R/pmcmc_state.R	100.00% <100.00%> (ø)
R/predict.R	100.00% <100.00%> (ø)
R/trajectories.R	100.00% <100.00%> (ø)

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[richfitz]

This was read for review, until the that last version bump, which looks to have done something terrible to the version of dust installed; looks like remotes decided it would "upgrade" dust to a previous version on the logs. I'll open a separate PR that updates this to new actions, but in the meantime I think this is still ok to look at