[llvm-symbolizer][test] Rename and tweak tests using llvm-symbolizer

Prior to this change, there are a few tests called llvm-symbolizer* in
the DebugInfo test area. These really were testing either the DebugInfo
or Symbolizer library, rather than the llvm-symbolizer tool itself, so
this patch renames them to be clearer that they aren't explicitly tests
for llvm-symbolizer (such tests belong in test/tools/llvm-symbolizer).

This patch also reinstates the copying of a DWO file, removed previously
in r352752. The test needs this so that it could possibly fail.

Finally, some of the tests have been simplified slightly by removing
unnecessary switches and/or unused check-prefixes.

Reviewed by: dblaikie

Differential Revision: https://reviews.llvm.org/D57518

llvm-svn: 352847