Kokkos build and numerics support

[rochi00]

This PR adds the first upstreamable slice of libMesh Kokkos support: build-system integration for .K translation units plus
standalone Kokkos numerics oracle tests.

The scope is intentionally limited to:

• Kokkos-aware build support for libMesh tests
• device-safe numerics support in core vector/tensor types
• standalone Kokkos numerics oracle coverage
• generated autotools updates as a separate final commit

[moosebuild]

Job Coverage, step Generate coverage on 4263dfc wanted to post the following:

Coverage

	cc8438	#4451 4263df
	Total	Total	+/-	New
Rate	65.60%	65.60%	-	100.00%
Hits	78611	78611	-	6
Misses	41227	41227	-	0

Diff coverage report

Full coverage report

This comment will be updated on new commits.

[roystgnr]

We're definitely getting there. I'd say the only thing that really ought to be fixed now is the error macro forwarding direction and (unless there's a good reason not to that I'm missing) the function redundancies.

[roystgnr]

Make system and error handling look good to go now!

We've still got more duplication than we want in the math operators, though; not all of the "an operator which just shims a custom-named function that doesn't need to exist separately" cases are gone, and there's some more subtle "N operators shim a custom-named function" cases than could be turned into "N-1 operators call the one of them that now has the implementation in it".

[roystgnr]

Split all commits like this in two in the future - the stuff we actually change in the first, and the stuff that bootstrap (or autoreconf, however you do it) changes in the second.