Adds postprocessor to track time step number for transient problems

framework/doc/content/source/postprocessors/NumTimeSteps.md

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+# NumTimeSteps
+
+!syntax description /Postprocessors/NumTimeSteps
+
+## Example Input Syntax
+
+!listing /test/tests/postprocessors/num_time_steps/numtimesteps.i block=Postprocessors
+
+!syntax parameters /Postprocessors/NumTimeSteps
+
+!syntax inputs /Postprocessors/NumTimeSteps
+
+!syntax children /Postprocessors/NumTimeSteps

framework/include/postprocessors/NumTimeSteps.h

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+//* This file is part of the MOOSE framework
+//* https://www.mooseframework.org
+//*
+//* All rights reserved, see COPYRIGHT for full restrictions
+//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
+//*
+//* Licensed under LGPL 2.1, please see LICENSE for details
+//* https://www.gnu.org/licenses/lgpl-2.1.html
+
+#pragma once
+
+#include "GeneralPostprocessor.h"
+
+/**
+ * Reports on the number of time steps already taken in the transient
+ */
+class NumTimeSteps : public GeneralPostprocessor
+{
+public:
+  static InputParameters validParams();
+
+  NumTimeSteps(const InputParameters & parameters);
+
+  virtual void initialize() override {}
+  virtual void execute() override {}
+
+  /**
+   * This will return the current time step number.
+   */
+  virtual Real getValue() const override;
+
+protected:
+  FEProblemBase & _feproblem;
+};

framework/src/postprocessors/NumTimeSteps.C

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+//* This file is part of the MOOSE framework
+//* https://www.mooseframework.org
+//*
+//* All rights reserved, see COPYRIGHT for full restrictions
+//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
+//*
+//* Licensed under LGPL 2.1, please see LICENSE for details
+//* https://www.gnu.org/licenses/lgpl-2.1.html
+
+#include "NumTimeSteps.h"
+#include "FEProblem.h"
+
+registerMooseObject("MooseApp", NumTimeSteps);
+
+InputParameters
+NumTimeSteps::validParams()
+{
+  InputParameters params = GeneralPostprocessor::validParams();
+  params.addClassDescription("Reports the timestep number");
+  return params;
+}
+
+NumTimeSteps::NumTimeSteps(const InputParameters & parameters)
+  : GeneralPostprocessor(parameters), _feproblem(dynamic_cast<FEProblemBase &>(_subproblem))
+{
+}
+
+Real
+NumTimeSteps::getValue() const
+{
+  return _feproblem.timeStep();
+}

test/tests/postprocessors/num_time_steps/gold/numtimesteps_out.csv

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+time,timestep_ctr
+0,0
+0.001,1
+0.002,2
+0.003,3
+0.004,4
+0.005,5
+0.006,6
+0.007,7
+0.008,8
+0.009,9
+0.01,10

test/tests/postprocessors/num_time_steps/numtimesteps.i

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+[Mesh/gmg]
+  type = GeneratedMeshGenerator
+  dim = 1
+[]
+
+[Postprocessors/timestep_ctr]
+  type = NumTimeSteps
+[]
+
+[Problem]
+  solve = False
+[]
+
+[Executioner]
+  type = Transient
+  dt = 0.001
+  num_steps = 10
+[]
+
+[Outputs]
+  csv = true
+  exodus = false
+[]

test/tests/postprocessors/num_time_steps/tests

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+[Tests]
+  issues = '#29127'
+  design = 'NumTimeSteps.md'
+  [num_time_steps]
+    type = 'CSVDiff'
+    input = 'numtimesteps.i'
+    csvdiff = 'numtimesteps_out.csv'
+    requirement = 'The postprocessor shall be able to count the number of time-steps that have been taken '
+                   'over the course of the simulation of a transient.'
+  []
+[]