Add IDA Stat struct

[alexander-novo]

Description

Adds a new structure, IdaStats, which keeps track of several statistics returned by IDA. A user can query these statistics from IDA by calling Ida::getStats() and can accumulate several runs of stats in the structure. There is also functionality to print a report, similar to the Ida::printFinalStats() function after the stats have been accumulated together.

Closes #322

@Steven-Roberts let me know if there's anything else you think I should put in.

Proposed changes

It makes sense for Ida::getStats() to be const, but then Ida::checkAllocation() and Ida::checkOutput() are inaccessible. These functions never touch any IDA state, so it makes sense for these functions to be static anyway.

Checklist

• All tests pass.
• Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
• The new code follows GridKit™ style guidelines.
• There are unit tests for the new code.
• The new code is documented.
• The feature branch is rebased with respect to the target branch.
• I have updated CHANGELOG.md to reflect the changes in this PR. If this is a minor PR that is part of a larger fix already included in the file, state so.

There are not unit tests, but I have added a printout of the report to the rlcircuit example:

                         Steps :           70
                Residual evals :           86
         Linear decompositions :           19
           Error test failures :            0
                 Linear solves :           86
Nonlinear convergence failures :            0

Further comments

[Steven-Roberts]

@Steven-Roberts let me know if there's anything else you think I should put in.

This looks like a reasonable set of stats to start with.

[pelesh]

A couple of minor things to fix before this could be merged, otherwise very helpful. Thanks!