WIP: add SCR to HDF path

[adammoody]

This starts the work to integrate SCR into the (synchronous) HDF checkpoint path. Since the HDF path writes a single shared file, one would need to run SCR in bypass mode:

SCR_CACHE_BYPASS=1

This is not yet complete.

• The string manipulation to compute the file suffix needs to be fixed.
• The getDt path for HDF needs to include SCR calls. I updated getDt to show the SCR calls for HDF, but I dropped the existing SCR getDt code. That would need to be added back, but we'll need a new compile time guard.

Also updated this PR to include SCR in the non-HDF, single file path.