fix Issue 10141 - wrong error message with Tuple!(int) : Error: static assert "Cannot put a char[] into a Appender!(string)"

Essentially it's bad code if it branches based on the condition `global.errors != 0`.
Merge pull request #2346 from 9rnsr/fix10141

Issue 10141 - wrong error message with Tuple!(int) : Error: static assert "Cannot put a char[] into a Appender!(string)"
Add support for getting unit tests from aggregate.
Add unit tests for __traits(getUnitTests).
Add const and better documentation to collectUnitTests.
Merge pull request #2328 from jacob-carlborg/getUnitTests_tests

Unit tests for __traits(getUnitTests)