Implement device functions to simplify writing kernel code [v2]

[fwyzard]

Implement device functions to simplify writing kernel code:

• oncePerGrid(acc);
• oncePerBlock(acc);
• uniformElements(acc, size) and uniformElements(acc, begin, end);
• uniformGroups(acc, size) and uniformGroupElements(acc, group, size);
• independentGroups(acc, groups) and independentGroupElements(acc, group_size);
• variations of these functions along different dimensions.

Implement tests for the most common functions.

[fwyzard]

I'm starting to hate Visual Studio...

D:\a\alpaka\alpaka\test\unit\exec\src\Once.cpp(133): FAILED:
  REQUIRE( *status == true )
with expansion:
  true == true

[fwyzard]

@psychocoderHPC all CI tests are finally happy... I can go on vacation :-)

[ikbuibui]

Sorry to comment on a merged PR, was there any reason why makeWorkDiv() was put in test/unit/exec/src? It seems like a useful interface

[fwyzard]

The current implementation makes some assumptions on how to us thread and elements. I have no problem moving it to a central place, but I don't know what @psychocoderHPC and @SimeonEhrig think of it.

[ikbuibui]

I noticed it also doesnt check if the work div is valid, correct? because elements can be greater than maxThreadsPerBlock

[fwyzard]

It's certainly possible.