Steady state callback

[LasNikas]

I tested the callback with the pipe_flow_2d.jl example. It terminates after ~0.8sec.
I consider the change in kinetic energy in a 0.002*10 interval.

pp_callback = PostprocessCallback(; dt=0.02, kinetic_energy)

steady_state = SteadyStateCallback(; dt=0.002, interval_size=10, abstol=1.0e-8, reltol=1.0e-6)

[codecov]

Codecov Report

Attention: Patch coverage is 52.94118% with 32 lines in your changes missing coverage. Please review.

Project coverage is 68.47%. Comparing base (c744cad) to head (3618976).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/callbacks/steady_state_reached.jl	45.76%	32 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #601      +/-   ##
==========================================
- Coverage   68.71%   68.47%   -0.25%     
==========================================
  Files          86       87       +1     
  Lines        5299     5360      +61     
==========================================
+ Hits         3641     3670      +29     
- Misses       1658     1690      +32     

Flag	Coverage Δ
unit	68.47% <52.94%> (-0.25%)	⬇️

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[svchb]

There is one mistake in the condition since you pop/push the current ekin one value is always 0.0 which will effectively reduce the interval size by one.

[efaulhaber]

Please use terminate! and then we wait for the next release of StrideArrays.jl to be able to use the latest version of DiffEqCallbacks.jl, which fixes the error.

Also, this PR is missing a test. I think it should be sufficient to run the hydrostatic water column with the steady state callback, once with interval and once with dt.