[Clang][Coroutine][DebugInfo] Relax test ordering requirement

The test added in D97533 (and modified by this patch) has some overly
strict printed metadata ordering requirements, specifically the
interleaving of DILocalVariable nodes and DILocation nodes. Slight changes
in metadata emission can easily break this unfortunately.

This patch stops after clang codegen rather than allowing the coro splitter
to run,  and reduces the need for ordering: it picks out the
DILocalVariable nodes being sought, in any order (CHECK-DAG), and doesn't
examine any DILocations. The implicit CHECK-NOT is what's important: the
test seeks to ensure a duplicate set of DILocalVariables aren't emitted in
the same scope.

Differential Revision: https://reviews.llvm.org/D100298