Support for custom interpolation procedure using FindPointsGSLIB.

[kmittal2]

PR	Author	Editor	Reviewers	Assignment	Approval	Merge
#4270	@kmittal2	@tzanio	@vladotomov + @SchmidtMat	5/11/24	⌛due 5/25/24	⌛due 6/1/24

PR Checklist

• Code builds.
• Code passes make style.
• Update CHANGELOG:
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• Update INSTALL:
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• New capability:
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• Update this checklist, if the new pull request affects it.
• Run make unittest to make sure all unit tests pass.
• Run the tests in tests/scripts.
• (LLNL only) After merging:
  • Update internal tests to include the new features.

[tzanio]

This PR is now under review (see the table in the PR description). To help with the review process, please do not force push to the branch.

[vladotomov]

Suggested change

	* is located on. Then, interpolation can be done locally by the user before
	* is located on. Then, custom interpolation can be defined locally by the user before

[vladotomov]

Comment how the int_vals should be structured. And shouldn't it be const?

[vladotomov]

Both Send... functions send and receive at the same time, maybe Distribute... is a better name.

[vladotomov]

Comment how the returned Vector is arranged.

[vladotomov]

It would help to describe briefly the usual calling sequence:

FindPoints(...)
SendElementsAndCoordinatesToOwningMPIRanks()
Get...
Get...
...some computation...
SendInterpolatedValuesBack()

[vladotomov]

In this case the received values are stored as internal vectors and access through const getters. The other function returns a non-const Vector. Not sure why it's different, might be good to unify the setup of the received vectors (I'd do them all as temporary if you don't need to store them internally).