Add TerminationException::what()

[roystgnr]

We're still not going to inherit from std::exception and risk getting confused with other descendants of it, but having a basic what() message is what our --disable-exceptions version of LIBMESH_THROW was expecting, and this seems like the best way to fix those builds.

This should fix the devel->master merge "No Exceptions" CI recipe broken by #4369.

[roystgnr]

I'm adding the "No Exceptions" recipe to CI here.

Normally I'd be in a rush to merge without waiting for PR-level CI right now, since we want all the devel->master recipes to be passing before we use a libMesh hash for a MOOSE submodule update, but since MOOSE never disables exceptions we've decided to make the "No Exceptions" recipe a special case. An irregularity. A non-conformity.

[moosebuild]

Job Coverage, step Generate coverage on 0302afb wanted to post the following:

Coverage

	dcacb2	#4375 0302af
	Total	Total	+/-	New
Rate	65.30%	65.30%	-0.01%	-
Hits	77565	77559	-6	0
Misses	41210	41216	+6	0

Diff coverage report

Full coverage report

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