Initial SplineR2R offload

[ye-luo]

Proposed changes

Initial implementation.

What type(s) of changes does this code introduce?

• New feature

Does this introduce a breaking change?

• No

What systems has this change been tested on?

epyc-server

Checklist

• Yes. This PR is up to date with current the current state of 'develop'
• Yes. Code added or changed in the PR has been clang-formatted

[ye-luo]

Test this please

[ye-luo]

Test this please

[ye-luo]

Test this please

[PDoakORNL]

I feel like there is some coverage missing here that would be nice to have, although its in keeping with the spotty coverage throughout the SplineX2X files.
The missing coverage for
SplineR2R<ST>::mw_evaluateDetRatios()
and one of the legs of the
const ST signed_one = (bc_sign & 1) ? -1 : 1;
being my only real concern with this PR.

[ye-luo]

Test this please

[ye-luo]

Test this please

[ye-luo]

Test this please

[ye-luo]

I feel like there is some coverage missing here that would be nice to have, although its in keeping with the spotty coverage throughout the SplineX2X files. The missing coverage for SplineR2R<ST>::mw_evaluateDetRatios() and one of the legs of the const ST signed_one = (bc_sign & 1) ? -1 : 1; being my only real concern with this PR.

Both covered with the newly added unit test based on LiH-x.