Generalize DebugInfo tests by avoiding explicit metadata numbers

This addresses several (not all) debug info tests that use explicit metadata
numbers. Wherever the same number appeared more than once in a test I used
a named match to ensure the same number appeared in all those cases (this may
still be overly constraining test cases as they may not have actually cared
about that relationship). For one-off numbers I just replaced them with an
unnamed regex.

This may underconstrain poorly written test cases that were interested in
checking that certain metadata nodes were related but didn't actually match
on all the related nodes numbers.

llvm-svn: 174247