Backend Changes to Make PBC ACForces Correct

[rcclay]

Please review the developer documentation
on the wiki of this project that contains help and requirements.

Proposed changes

Closes issue #4583

Series of backend changes to ensure Assaraf-Caffarel force estimators work in periodic boundary conditions at gamma and non-trivial twists. Consists of 1.) updating force specific LCAO calls to correctly handle nonzero-twists, and 2.) fixing real/complex issues in the NonLocalECPComponent fast force evaluations. Unit tests based on finite differences for NonLocalECP and Kinetic energy derivatives added for C-diamond at 1/4,1/4,1/4 kpoint.

Bug fixes for slower legacy implementation not added because of expected deprecation of these routines.

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

Delete the items that do not apply

• Bugfix
• New feature
• Build related changes
• Testing changes (e.g. new unit/integration/performance tests)

Does this introduce a breaking change?

• No

What systems has this change been tested on?

Intel Xeon, RHEL7

Checklist

Update the following with a yes where the items apply. If you're unsure about any of them, don't hesitate to ask. This is
simply a reminder of what we are going to look for before merging your code.

• 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
• Yes. This PR adds tests to cover any new code, or to catch a bug that is being fixed
• N/A. Documentation has been added (if appropriate)

[rcclay]

Mixed precision complex is having issues on kinetic energy force component fkin[1][2]. Investigating.
All good

[ye-luo]

Bug fixes for slower legacy implementation not added because of expected deprecation of these routines.

Which routines of what classes were you referring to?

[rcclay]

@ye-luo Both NonLocalECPComponent::evaluateOneWithForces() functions. These use the naiive ion derivative algorithm, and are just a real pain to maintain.

[ye-luo]

Test this please