Td adjoint

[yardasol]

Description

This PR adds machinery for time-dependent adjoint calculations toward the goal of generating time-dependent FW-CADIS weight windows. In particular, this PR:

• Adds machinery to store the forward flux (and precursors) over a forward time-dependent simulation to use as the fixed source in an adjoint time-dependent simulation
• Adds a setting to detect if an FW-CADIS simulation needs that eigenvalue modification (turning off fission in the adjoint simulation)
• Adds machinery to allow time-dependent fixed source strengths.
• Adds machinery to write a weight_windows.h5 file for each timestep, if desired.
• Adds tests for FW-CADIS eigenvalue weight windows
• TODO: add tests for TD FW-CADIS, TD MAGIC weight window generation (maybe wait for time census PR to do this?)
• TODO: add documentation on the time-dependent adjoint
• TODO: add documentation on FW-CADIS eigenvalue mode.

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 15) on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)