[WIP] Add full test case for variadic delayed Matrix allocation

[devreal]

@fuchsto: Please have a look at this. Your test MatrixTest.DelayedAlloc succeeds while the new test MatrixTest.VariadicDelayedAlloc fails while checking the validity of the pattern arguments, which are the same as in the first test. So either the first test case is invalid or the check in PatternArguments is overly strict. I cannot decide that :)

[devreal]

Hmpf, the error is not triggered in CI. Here is what I see on my laptop:

[= -1 LOG =]               TestBase.h : 251 | ===> Running test case MatrixTest.VariadicDelayedAlloc ...
[=  1 LOG =]               TestBase.h : 254 | -==- DASH initialized with 4 units
[    1 ERROR ] [  9679 ] PatternArguments.h       :280  | dash::exception::InvalidArgument             | [ Unit 1 ] Pattern arguments invalid: Mixed distribution types
[  ERROR   ] [UNIT 1] in [=  1 LOG =]               TestBase.h : 264 | -==- Test case finished at unit 1
[=  1 LOG =]               TestBase.h : 267 | -==- Finalize DASH at unit 1
[= -1 LOG =]               TestBase.h : 272 | <=== Finished test case MatrixTest.VariadicDelayedAlloc with 4 units

[ddiefenthaler]

I can report the same error, for me it even triggers in the first test MatrixTest.DelayedAlloc.
It occurs in a 32bit VM, only when run with 4 or 6 units.

I tried to debug it a little bit and it seems to fail in check_tile_constraints() of PatternArguments.h#L265.
The distribution passed down seems to be [NONE, TILE(5), TILE(3)].

[devreal]

The main issue has been fixed in #444 (thanks to @fmoessbauer). What is left in this PR is splitting the test for variadic matrix allocation into a separate test case.