Issue a retry when X is invalid after a hydro update

[maxpkatz]

PR summary

(rho X) can be negative after a hydro update even if rho itself is not, for example due to transverse terms being applied near sharp composition gradients. We should retry with a smaller timestep in that scenario.

PR motivation

Closes #1952

PR checklist

• test suite needs to be run on this PR
• this PR will change answers in the test suite to more than roundoff level
• all newly-added functions have docstrings as per the coding conventions
• the CHANGES file has been updated, if appropriate
• if appropriate, this change is described in the docs

[maxpkatz]

This should address one of the two failure modes identified in #2096 (although it could still lead to an abort if too many subcycles are needed to resolve the problem).

[zingale]

tests: http://groot.astro.sunysb.edu/Castro/test-suite/gfortran/2022-04-23-001/index.html