test/DebugInfo/X86/dbg-value-isel.s: correct lexical block descriptor to match schema

This silently broke a long time ago when I unified some aspects of the
debug info schema. I'm just cleaning these up if/when they become a
problem.
DebugInfo: Refactor some tests to allow DW_AT_name to not be the first attribute in a local variable.

In an effort to fix concrete variables referencing abstract origins
where the concrete variable preceeds the first inlined usage, the
addition of attributes such as name, file, etc will be delayed until the
end of the module (to wait to see if any inlined instances have
occurred, thus necessitating an abstract definition that the concrete
definition should also reference).

These test cases don't actually need to care about this ordering of
attributes, so update them to be more resilient to such changes coming
in the near future.